Ingredients :

• Gruyère (or Comté) — This is the centerpiece. Get a real block and grate it yourself — bagged Gruyère is often too dry and melts poorly. Comté also works, being slightly sweeter. If you can’t find it, Swiss Emmental is okay, but add a handful of parmesan to regain that nutty edge.
• Turkey ham — Cut it into cubes yourself from thick slices rather than buying pre-cut sticks. The texture is better — neither too soft nor too dry. Chicken ham also works if that’s what you have on hand.
• Whole milk — Whole milk, seriously. Semi-skimmed works, but the sauce is less silky. Most importantly, heat it before adding it to the roux — this prevents lumps and speeds up thickening.
• Nutmeg — A pinch, not a teaspoon. Nutmeg in a béchamel is almost invisible — but without it, you feel something is missing. Freshly grated if possible; the difference is real.