Not many dishes have a proper birthday, but gratin dauphinois was first officially served in the Dauphinois town of Gap on 12 July 1788, as an accompaniment to the ortolans served by Charles-Henri, Duke of Clermont-Tonnerre. In its way, it was a bold statement as potatoes in France had only recently been considered edible, thanks to the hard work of Antoine Augustin Parmentier.
Unlike many dishes, the potatoes are raw, but sliced very thinly and layered in a buttered casserole dish, then baked with cream or milk. Many chefs add gruyère, although that officially makes it a gratin savoyard.
Other names you may see for the same thing are pommes de terre dauphinoise, potatoes à la dauphinoise and gratin de pommes à la dauphinoise. But don’t confuse it with pommes dauphine.
Image by GeeJo on Wikimedia Commons