Ingredient

Roast potatoes

A great roast potato has an enormous, ragged, crisp surface and a fluffy interior. Both come from one step that takes ten seconds and that most people skip: shaking the parboiled potatoes hard enough to rough up their outsides.

Why roughing up works

Crisping requires surface area and dryness. A smooth peeled potato has very little of the first. Parboiling softens the outer few millimetres, and shaking the drained potatoes breaks that softened layer into a rough, floury coating of loose starch and broken cells.

In hot fat that coating dehydrates and browns into something far crisper than the potato surface could ever have become on its own. It is the difference between a roast potato and a baked one.

It only works with floury potatoes. A waxy potato does not develop the soft, mealy outer layer, so there is nothing to rough up.

The method

1. Peel floury potatoes and cut them into large, uneven chunks. Uneven is deliberate — corners and flat faces are where the crisp happens.
2. Boil in well-salted water until genuinely soft on the outside and a knife goes into the edge easily. Slightly over is better than under.
3. Drain and leave them in the colander for a couple of minutes to steam dry.
4. Put the lid on the pan and shake them hard, several times. The outsides should look visibly fluffy and broken up.
5. Meanwhile get the fat properly hot in the tin, in a hot oven — 200–220°C. It should shimmer.
6. Lower the potatoes in carefully and turn each one to coat. They should sizzle immediately. Give each one space.
7. Roast for around 45 minutes to an hour, turning once or twice. Do not fuss with them, and do not add salt until near the end.

The fat

Goose or duck fat

The classic. High smoke point, excellent flavour, and it crisps beautifully.

Beef dripping

Arguably better than goose fat and much cheaper. The traditional English choice.

Vegetable or sunflower oil

Works perfectly well. Neutral, high smoke point, no flavour of its own.

Olive oil

Fine, though extra virgin is wasted at this temperature and can taste bitter.

Butter

On its own, no — it burns. A knob added for the last ten minutes adds flavour.

Why they go soggy

• Crowded tin. They steam each other. Use two tins rather than one full one.
• Fat not hot enough. They absorb it rather than frying in it.
• Wet potatoes. Steam-dry them properly before they go in.
• No parboil. The outside never gets the mealy layer that crisps.
• Oven too cool. 200°C minimum, and preheated properly.
• Salted too early. Salt draws moisture to the surface. Season near the end.
• Full diagnosis on the soggy roast potatoes page.

Which potato, and why it matters more than anything else

The variety decides the outcome before any technique is applied. A waxy potato cannot be made to roast like a floury one.

Maris Piper

The default in the UK, and it is the default for good reason. Floury enough to fluff, firm enough to hold.

King Edward

Slightly drier and floury. Excellent, and a little more prone to falling apart at the parboil.

Rooster and Desiree

Reliable all-rounders with a firmer result.

Russet / Idaho

The floury standard elsewhere, and very good.

Charlotte, Jersey Royal, Anya and other waxy potatoes

They will roast and they will never fluff. Good roasted whole in their skins; wrong for a crisp roastie.

New potatoes

A different dish entirely, and an excellent one. Do not parboil and rough them up.

If you do not know what you have

Cut one and rub the cut faces together. Floury potatoes feel chalky and grip; waxy ones feel wet and slip.

Common questions