Open the oysters and reserve the hollow shells. Wash and dry the shells thoroughly. Place the oysters on a lightly buttered, peppered baking dish (no salt). Warm the oysters and shells in the oven without fully cooking them.
Sweat the finely chopped shallot in a bit of butter. Add the mushroom duxelles, season to taste, and stir in a dash of grated nutmeg.
Combine the hollandaise sauce with the chive sauce. Gently cook for 5 minutes, then strain just before serving. Fold in two tablespoons of whipped cream.
Blanch the seaweed in boiling water, drain, and divide among the bottoms of four plates.
Arrange six shells per plate. Fill with warm mushroom duxelles, top with the warmed oysters, and cover with sauce. Glaze under a salamander or grill.
Garnish with finely chopped chives.
Mousseline Sauce (Dutch Sauce Base):
Heat the heavy cream in a saucepan until simmering.
In a separate pan, whisk the egg, then gradually add the hot cream, starting with spoonfuls while whisking constantly.
Once 5 spoonfuls are incorporated, cook over very low heat, adding remaining cream while stirring.
Season with squeezed lemon, salt, and pepper. Simmer gently for a few minutes.
Chive Sauce:
Finely chop the shallot and chives. Crush the peppercorns in a cloth using a plate or saucepan.
Reduce the alcohol vinegar with the crushed peppercorns and shallot by 3/4 over about 5 minutes. Cool off the heat.
Add the crème fraîche to the cooled reduction, then stir in chopped chives. Season with salt at the end.
Breton oysters from Prat-ar-Coum offer an unparalleled flavor. Find them online at https://yfrog.com/5mhutres2d.
Duxelles recipe available in our archives: https://www.recettes-hubert.com/?s=Merlan+bleu
