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As Christmas rushes towards us, I wanted to nail my roast potatoes once and for all. And although roasting a potato is a seemingly basic task, I still had questions. Questions such as: am I right to default to Maris Pipers? Does the way you cut your potatoes make a difference? Is goose fat truly the gold standard? Is preheating the fat before adding the potatoes strictly necessary? And more besides.
And so, in this week’s small win I share what I discovered in the course of my roast potato experiments — and I answer all of those questions. Because it is my hope that these tips will help you to enjoy fabulous roast potatoes for years to come.
Love, Alexina
The last few bits of 2024 — Next week it’s the December giveaway for paid subscribers with a juicy prize worth over £220 (and there’ll be a little Christmas offer on annual paid subscriptions too, so stay tuned). And in the final small win of 2024, I’ll be sharing my ode to the humble cranberry.
Coming up in 2025 — The best chocolate sauce happens to be vegan. The vinaigrette that all my friends go wild for. The delicious and nutritious 20-minute meal that I make every week. The forgotten pancake. Plus 101s on vegetarian cooking, savoury ways with eggs and date-night cooking. Lots of good stuff.
Q1: WHICH POTATO VARIETY?
The classic option is the trusty Maris Piper and, look, it’s a solid one — the very last thing I’d want to do is give you any sort of complex about this.
Still, if you are a Sainsbury’s shopper, I feel that it’s my duty to let you know about a potato that is nicknamed ‘the butterless baker’. It’s a variety called Vivaldi that’s sold as part of the Taste The Difference range (you can get it in standard, salad potato and baking potato form) and thus is available consistently all year round.
My mum discovered the Vivaldi baking potatoes many years ago and honestly, they’re the best: they have the softest, fluffiest texture and a sweet creamy flavour that is quite addictive. When I want buttery mash, or beautifully soft-on-the-inside, crispy-on-the-outside roast potatoes, Vivaldis are my secret weapon.
The wonderful world of potatoes
There are plenty of potato varieties beyond Maris Piper and Vivaldi, and I just had to share this very joyful thing that I received from one of my lovely paid subscribers, Rebecca: her taste notes on different potato varieties!
Different potatoes will work best for different preparations, but I am super keen to try Georgina and Manitou potatoes asap! The potato variety — if not called out in the ‘title’ — can be found in the little white box on the front of the packet.
By the way, Rebecca runs Glasgow-based microbakery Maple Leaf which just won Scotland’s Best Croissant!
Q2: DOES IT MATTER HOW I CUT THE POTATOES?
How you cut the potatoes is hardly make or break but, speaking in ideal-world terms, there are a couple of things you’re trying to achieve:
Produce pieces of a roughly even size and shape
Maximise the flat surface area of each piece
These two aims don’t fit perfectly together because if you were to only maximise the flat surface area, you would end up with unatttractive and uneven shaped pieces. Case in point:
Still, there’s a happy medium to be had and, I promise, it’s not faffy (even though I’ve overintellectualised it here).
The point, really, is that most potatoes are best cut into three, and when making those cuts you want to angle the knife slightly (rather than go in straight). Like this:
As you cut the potatoes, add them directly to a large pan filled with water to stop them from oxidising. The potatoes can hang out in the water for a couple of hours or even overnight before being parboiled.
Q3: HOW SALTY SHOULD THE WATER BE?
It took a while but I think most of us have now internalised the mantra of nonnas the world over that your pasta water really ought to be “as salty as the sea”.
And whilst the water should never be quite that salty in practice, the spirit of the expression — which is to salt generously — is true. So true, in fact, that it shouldn’t only apply to pasta: it’s best to generously salt the water of almost any food that you boil, but especially potatoes!
You can add salt to your potatoes as you roast them, or even once they are roasted, but you’ll get a more delicious result if you season them from the inside out, i.e. through the water.
And this is a lesson for all cooking: seasoning early in the process is far more effective at teasing out the inherent flavour of an ingredient than seasoning at the end.
Here is the ratio of salt to water that I use when boiling pretty much anything:
1 tbsp Diamond Kosher salt (or flaky sea salt)* per 1 litre of water
*Or 1/2 tbsp if using fine sea salt!
Not all salt is equally salty
Inconvenient but true. 1 tbsp of salt in 1 litre of water can taste more or less salty depending on the specific brand and form (fine vs flaky vs coarse) of the salt used.
I use Maldon salt for roasting and finishing dishes, but I like Diamond Kosher salt for seasoning meat and boiling things like pasta and potatoes. This is because:
It has a much gentler saltiness than your average salt, which makes it harder to overseason your food
Its fine texture makes it easier to season meat evenly
It dissolves quickly
It contains no iodine or additives
Conveniently, you can swap Maldon sea salt flakes and Diamond Kosher salt 1:1 on a volume basis (i.e. 1 tbsp Diamond Kosher salt = 1 tbsp Maldon sea salt flakes). This is because even though Maldon is much saltier, it’s less dense due to its flaky form.
If using fine sea salt — which is saltier than Diamond Kosher salt and just as dense — you need to use only half as much on a volume basis (i.e. 1 tbsp Diamond Kosher = 1/2 tbsp fine sea salt).
Q4: DOES ADDING BICARB REALLY MAKE A DIFFERENCE?
Left: potatoes par-boiled with bicarb; Right: potatoes boiled without bicarb
If the point of roast potatoes is crispiness, then it’s important to do all that you can to maximise texture on the potato’s surface.
As you’ll be able to see in the photo, a little bicarbonate of soda added to the water that the potatoes are boiled in goes a long way towards increasing the roughness of those edges.
How does it work? Well, potatoes contain pectin — the chemical compound that holds fruits and vegetables together (you can read more about pectin in my jam-making 101). Pectin breaks down when subjected to heat, but it’s also influenced by pH. Adding bicarbonate of soda turns the water alkaline, and this encourages the pectin in the potatoes to break down faster — which accounts for those raggedy edges in the photo. A 1/4 tsp of bicarb per litre of water does the trick and it’s such an effortless step that you would be mad not to!
Q5: MUST I GET AGGRESSIVE WITH MY ROAST POTATOES?
You must.
Rough’em up real good:
Rougher edges = crispier edges.
Q6: WHICH FAT SHOULD I USE?
I tested 4 types of fat — traditional goose fat, beef tallow, ghee and vegetable oil — and I was surprised by how much it influenced the flavour (although, needless to say, none of these produced bad tasting roasties).
Flavourwise, ghee and beef tallow were the standouts (goose fat was surprisingly underwhelming) — but a consideration of which fat to use isn’t only about flavour.
Let’s briefly talk about smoke points.
The smoke point of a fat is, as the term would suggest, the point at which that fat starts to smoke (i.e. burn). It’s a level you want to avoid (especially if you’ve just washed your hair).
Different fats have different smoke points and this comes into play when you’re cooking something at a high temperature with a decent quantity of fat — like roast potatoes.
I was interested to discover that the smoke point of goose fat is comparatively low, which correlated with my experience that it was quick to smoke out the kitchen (and therefore not so ideal for my roasties):
Source: The Professional Chef by The culinary Institute of America, via Serious Eats
Beef tallow — one of my favourites flavour-wise — was also quite quick to smoke out the kitchen, which makes sense when you learn that its smoke point is 205°C… a level below the 220°C oven temperature that we’re working with. So whilst I enjoyed the flavour it yielded, the smell and smokiness that it contributed to my home — and the risk that that smokiness could turn into an acrid flavour over an extended period in the oven — was a turn-off.
Meanwhile, ghee (or clarified butter, which is not the exact same thing but very much adjacent) behaved beautifully and no wonder: with a smoke point of 230°C there was minimal risk of burning, and you gained that rounded, buttery flavour too (it is a myth that you can increase the smoke point of normal butter by combining it with vegetable oil, by the way).
Needless to say, ghee turned out to be the model fat — and one that you might reasonably use for cooking endeavours beyond Christmas, unlike goose fat and beef tallow which I find often go to waste after the festive period.
One of the drawbacks of ghee is how expensive it has become (particularly if you buy the organic, grass-fed stuff), but you should know that it’s pretty straightforward to make clarified butter at home — so that’s an option worth considering. And, in all fairness, organic grass-fed beef fat or duck/goose fat would set you back almost as much.
Do you need to preheat your fat?
Contrary to a lot of the classic recipes out there, I’m going to actively advise that you don’t.
It is possible to achieve golden crispy potatoes without significantly preheating the fat, and this avoids a number of the pitfalls — namely burning the fat (which can lend an acrid flavour), burning yourself (because the fat is so hot that it spits when you add the potatoes) and smoking out your house (the last thing you need on Christmas Day).
I pop the roasting tin and tray in the oven for 2 to 3 minutes to melt/heat up the fat, then I add the potatoes and flip them over to make sure they’re all coated.
Q7: WHAT ABOUT THE EXTRAS?
I have stripped this roast potato recipe back to the bare necessities; however, feel free to riff on it!
Here are some extras that you could add:
1 to 2 tbsp coarse semolina, for extra crunchiness
Whole unpeeled garlic cloves, for extra flavour
Whole sprigs of rosemary, for fragrance and nostalgia
Or get creative! I could imagine whole spices working beautifully (so long as the oven temperature wasn’t too high).
THE PERFECT ROAST POTATOES
Beautifully golden, but taken before I had nailed cutting the potatoes properly — do as I say, not as I do
Serves 6 to 8
Ingredients
3 litres (3 quarts) water
1.5kg (3 1/2 lbs) Vivaldi (or Maris Piper) potatoes
1 or 2 roasting tin(s) — it’s not always practical at Christmas, but if you can avoid overcrowding the roast potatoes, you’ll get a better result
Method
Add the water to a large pot.
Peel and cut the potatoes into 2 to 3 even pieces (cut at an angle, to maximise the sharp edges because these = more crispy bits). Add them to the water as you go.
When ready to parboil the potatoes, add the salt and bicarbonate of soda to the pot. Bring to the boil and simmer until the potatoes slide off a sharp knife readily and are starting to look a bit soft at the edges, around 20 to 25 minutes.
If you care about your potatoes staying in one piece, then pay close attention towards the end of this time to avoid overcooking them. Vivaldis hold together better than Maris Pipers, so you have a wider margin for error.
Drain the potatoes and shake them about to rough them up (again, I find that Vivaldis can survive quite rough handling, whereas you have to be a bit more delicate with Maris Pipers). Place them aside to steam dry and cool.
Preheat the oven to 220°C/200°C fan/425°F/gas 7. This is the point at which to toss any herbs, spices or semolina through your potatoes.
Once the oven is hot, add the roasting tray(s) with the ghee into the oven for 2 to 3 minutes to melt / heat up.
Remove the tray(s) from the oven and carefully add the potatoes. Turn them potatoes over in the fat until coated then arrange them flat side down. Make sure they’re spread out over the roasting tray rather than crowded together. Roast in the oven (top shelf, ideally) for between 30 and 45 minutes, turning them over halfway through, until deeply golden and crisp. Test one and sprinkle with additional flaky sea salt, if needed/liked. Serve immediately.
Make ahead: Potatoes can hang out in the water overnight. They can also be parboiled the day before and left on the side, covered lightly with a tea towel.
How hot should your oven be?
Oven temperatures and fierceness vary from oven to oven, so trust your instinct if you feel like a lower (or higher!) temperature would be more appropriate here.
Additionally, if you’re cooking the roast potatoes in the oven along with other items, bear in mind that you’ll likely need to opt for a higher oven temperature to ensure that everything browns.
I've bought some Vivaldi potatoes!
Should really start calling you Dr Alexina the level of science cookery you bring