Ingredients :

• The endives — Choose medium-sized ones. An endive that’s too big stays firm at the core even after cooking. In season — autumn and winter — they are naturally less bitter. Remove the small hard cone at the base with the tip of a knife; that’s enough to calm their character.
• The smoked salmon — No need for overpriced salmon here — it’s going to cook for forty minutes in the oven, so its fine nuances will disappear anyway. Classic supermarket smoked salmon works perfectly. Get slices wide enough to wrap the endives neatly.
• The thick crème fraîche — Thick, really — not liquid. Heavy cream or liquid cream will soak the bottom of the gratin and the whole dish becomes watery. Thick crème fraîche holds up during cooking, coating and gratinating perfectly. If you want to lighten it up, half thick cream and half Greek yogurt works well.
• The lemon — Juice and zest, both without exception. The zest brings the fragrance, the juice brings the acidity that balances the fat of the cream and the salt of the salmon. Start with half a lemon and taste before adjusting — it’s better to add more than to over-acidify everything at once.