1. Prepare a béchamel sauce. Melt 25 g of butter in a saucepan. Sprinkle the flour and cook for 2 minutes, stirring constantly. Remove from heat and add the cold milk all at once, whisking continuously. Bring to a boil over low heat, whisking constantly, then let cool.

2. Preheat the oven to 200°C.

3. Peel and finely chop the shallots. Place them in a saucepan and pour in the white wine. Cook over low heat until the liquid has almost completely evaporated.

4. Flake the crab meat into the shallot saucepan, add 50 ml of cognac, and heat for 1 minute; flambé. Once the flames have extinguished, stir in the cream and cook over high heat until thickened. Remove from heat and add the béchamel sauce, mixing well. Season with salt, pepper, and Cayenne pepper to taste.

5. Butter 4 gratin dishes. Divide the preparation among them. Sprinkle with Parmesan cheese. Bake in the oven until the surface is golden brown. Serve immediately.