In skillet, melt butter; saute mushrooms until lightly browned. Add garlic, cream, lemon juice, salt, pepper and nutmeg. Cook, stirring constantly, until cream thickens and its volume is reduced by half. Divide mushroom mixture and spoon over toast. Sprinkle each serving with 1/2 tablespoon parsley. Bake at 450° for 5-8 minutes or until sauce is bubbly. Serve immediately.