Ingredients :

• The eggs — Six for four people — enough for the dish to be generous, but not too many so that the béchamel remains the true protagonist. Size M or L, it doesn’t matter. What counts: they must be fresh so the whites hold up well when cut.
• Whole milk — Whole, not semi-skimmed. The difference in the texture of the béchamel is real: richer, more enveloping, it clings better to the eggs. Semi-skimmed gives a sauce that slides off instead of coating.
• Butter — No margarine, no oil. Butter melts differently, cooks differently, and smells differently. It’s what gives that nutty scent to the roux. Preferably unsalted to keep control over the salt levels.
• Grated cheese — Emmental is good, Comté is better. Its bolder taste stands up to the béchamel and gives a more complex crust. Gruyère if you have it, or a mix of the three. Avoid industrial pre-grated pizza cheese — it doesn’t really gratinate, it just melts into a dull mass.