A handful at a time, twist the mushrooms into a ball in the corner of a towel to extract their juice. Sauté the mushrooms in hot butter with the shallots or onions for 7 to 8 minutes, until the pieces begin to separate from each other.
Sprinkle on the flour and stir over moderate heat for 3 minutes.
Stir in the wine and boil for a minute. Then stir in two thirds of the cream. Add the seasonings. Simmer for 2 to 3 minutes, adding more cream by spoonfuls if the mushroom mixture becomes too thick. Correct seasoning and set aside.
Just before serving, reheat the mushrooms, pastry shells, and eggs. Put 2 or 3 tablespoons of the mushroom mixture into each shell, lay an egg over it, and coat with the sauce. Serve immediately on a platter or individual serving plates.