Thinly sliced potatoes baked slowly in milk and cream with garlic, until soft underneath and golden on top.
What makes it gratin dauphinois
Waxy potatoes, sliced thin and not washed.
Milk and cream, and a dish rubbed with garlic.
No cheese, if you follow the Dauphiné.
Where it comes from
It comes from the Dauphiné, the old province around Grenoble, and is often said to be one of the older potato dishes in French cooking. The potatoes aren't rinsed, so their starch thickens the milk and cream.
Its keepers insist there's no cheese and no egg in a true gratin dauphinois — cheese makes it something closer to a gratin savoyard. Many cooks add it anyway.
How it varies
Gratin savoyard
From Savoy, next door: with stock instead of cream, and cheese on top.