Combine butter, cream cheese and salt and beat well. Add flour and blend. Wrap dough in waxed paper 8x6 rectangle and chill overnight.
Remove 10 minutes before rolling. Roll part of dough at a time to 1/8 inch thick. Cut into 2 1/2 inch rounds. Put 1 teaspoon of filling in each.
Moisten edges and fold double. Press edges with fork to seal. Mix egg with milk and slightly beat. Brush with and milk and chill 1 hour. Bake at 350F for 25 minutes or until golden brown. May be frozen. Makes 5 dozen.
In pan, saute mushrooms and oinions in butter. Sprinkle in salt, pepper, lemon juice and flour. Stir and simmer 2 minutes.
Gradually add cream and stir util smooth and thickened. Chill. Add 1 tablespoon sherry or dry vermouth before chilling, if desired.