Why Restaurant Potatoes Are Better Than Yours

You can cut potatoes into chunks, coat them in oil and roast them.

They will be perfectly respectable.

They will also usually fail to develop that absurd restaurant crust that sounds slightly structural when your fork hits it.

The difference begins before the potatoes enter the oven.

Boiling them first changes the starch.

As potatoes cook in water, starch granules absorb water, swell and gelatinise. After draining, the exterior is no longer a smooth raw surface. It can be broken into a rough layer of softened starch.

That layer is extremely useful.

Shake the cooked potatoes around in the pot or bowl and their edges become ragged. You have just created more surface area.

More surface means more places for fat, dehydration and browning to do their work.

An alkaline cooking liquid can exaggerate the effect. Adding a small amount of baking soda raises the pH and encourages the outer structure of the potato to soften further, creating a starchy coating that can become exceptionally crisp when roasted. Controlled cooking tests by Serious Eats found the combination of boiling, alkaline water and roughing up the surface produced the crispest result.

Then comes the part home cooks often sabotage: space.

Crowd a tray and escaping water becomes steam around neighbouring potatoes.

Steam is useful for many things.

Creating a brittle roasted surface is not one of them.

The potatoes want fat, high dry heat and enough separation to lose moisture.

The result is a useful piece of culinary engineering.

The inside contains water and softened starch, giving you the fluffy centre.

The outside loses enough water to become rigid, browned and crisp.

That is why throwing raw potatoes into an oven with some olive oil can taste good but rarely produces the same architecture.

Restaurants are not hiding a secret ingredient.

They are simply willing to cook a potato twice.