FOLLOW the directions for cooking and shelling mussels. Cook the mushrooms as the basic recipe indicates; however, they should be sliced rather than left whole. Prepare the shrimp.
In a heavy saucepan, melt the butter and in it sauté the minced shallots until they are soft but not brown. Then add the white wine and the mussels, mushrooms, and shrimp. Simmer all together over low heat until only a little liquid remains in the bottom of the pan.
Meanwhile, in another saucepan, simmer the cream until it thickens. When it is almost of saucelike consistency, remove it from the fire and, with a sauce whisk, quickly beat in the egg yolks, one at a time. Add to this the mussel mixture, stir well together, and season lightly with salt and pepper. Fill the scallop shells and brown briefly in a hot (450' F.) oven.
