Dauphinoise Potatoes

• 450 g/1 lb potatoes, peeled
• butter
• salt and pepper

Slice the potatoes as finely as you can and slip them into cold water as you do so (this is not strictly necessary, but it helps to prevent discoloration, and washes off some of the starchiness which would make the final dish sticky. But if you like the stickiness - and many people do - don’t put them in water.)

Butter a shallow pie-dish. Drain the potatoes if they have been in water, a