Gratin de fruits de mer

03 — Method

1. Preheat the oven to 200 °C (400 °F) fan. Butter the 30 cm (12 in) gratin dish. Cut the cod into even 2 cm (¾ in) cubes.
2. Thaw the scallops on paper towels for 30 minutes and pat dry. Wipe the mushrooms and slice 5 mm (¼ in) thick.
3. Finely chop the 2 shallots. Remove the germ from the 3 garlic cloves and crush them. Chop half the parsley, keeping the rest to garnish.
4. Heat 30 g (1 oz) of butter in the large sauté pan over medium-high heat and sear the scallops for just 1 minute per side. Set aside.
5. In the same pan, soften the shallots for 2 minutes. Add the mushrooms and cook 5 minutes over high heat. Add the garlic and shrimp and cook 2 minutes until pink.
6. Deglaze with the white wine and reduce for 3 minutes. For the sauce, melt 60 g (2 oz) of butter in the saucepan, add the flour all at once and whisk into a pale roux.
7. Cook 1 minute, then whisk in the hot fish stock and cook 5 minutes until thick. Stir in the crème fraîche, nutmeg, salt and pepper. It should coat the back of a spoon.
8. Gently mix all the seafood, cod, drained mussels and sauce. Pour into the buttered dish, sprinkle with Gruyère and bake for 20 minutes at 200 °C (400 °F) until browned.