By tasting these Coquilles St Jacques you will congratulate yourself for taking the time to cook them
Mix the cheeses and reserve. In a small bowl, mix the egg yolk and cream and reserve.
In a medium saucepan, combine the scallops, wine, water, salt, pepper, parsley, bay leaf, thyme and shallots. Bring to a boil, lower the heat, cover and simmer for 5 minutes and immediately remove the pan from the heat.
Strain the scallops and broth through a sieve keeping the broth. Return the broth to the pot. Reserve the scallops.
Cook the broth over medium heat until approximately 1 cup of broth remains.
In the meantime, remove the scallops from the aromatics and cut 4. Reserve.
In a small skillet, melt 14 g (1 tbsp.) Of butter and cook the mushrooms for 5 minutes over medium-high heat, stirring constantly with a wooden spoon, until they begin to brown. Reserve.
In a medium saucepan, over low heat melt the remaining butter, remove the saucepan from the heat and whisk in the flour. Return the pan to the heat and cook for 1 minute . Remove the pan from the heat. Gradually whisk in the reduced broth and milk. Return the saucepan to the heat and cook over medium heat, stirring constantly with the wooden spoon, until the sauce thickens and sticks to the back of a spoon. Stir the egg cream mixture into the sauce and remove the pan from the heat. Add the lemon juice and Cayenne to the sauce, then the mushrooms and scallops.
Set the oven rack in the upper third of the oven and preheat the grill.
Divide the mixture among 4 shells or gratin dishes, cover with cheese, garnish the rim with rosette of mashed potatoes if desired. Place the shells on a baking sheet and cook under the grill until the cheese is golden.