Ingredients :

• The leeks — This is the aromatic heart of the dish. Choose medium-sized leeks — very large ones can be fibrous in the center. What really matters is melting them in a pan before assembling: translucent, almost caramelized, not just Wilted. If you skip this step, they will release water in the mold and your batter will be soggy.
• The salmon — Fresh or smoked, both work but give different results. Fresh salmon provides a firmer texture and a milder taste. Smoked salmon gives more aromatic power — but be careful not to over-salt the batter in that case. In practice, a mix of both is often the best compromise if you have both on hand.
• Crème fraîche — 20 cl of thick cream (heavy cream), not liquid. Thick cream holds up better during cooking and is what gives that melting, dense texture. If you use light liquid cream, the batter will be thinner, take longer to set, and will be less indulgent on the plate.
• Grated cheese — Emmental or Gruyère depending on what you have. Gruyère has a more assertive, slightly nutty taste, while Emmental is milder and stretches beautifully. Avoid soft cheeses — they would make the batter too wet. 50 grams is the right dose for flavor and a crust without overwhelming other flavors.