For tart shells, use 2 tablespoons butter to grease twenty-four 1-3/4-inch muffin pans. Using a 3-inch cookie cutter, cut rounds from bread. Press bread rounds evenly into muffin cups. Bake in a 400 degree F oven for 10 minutes. Remove from oven; set aside.
For filling, in a medium skillet, cook the green onions or the shallots in 2 tablespoons butter until tender, but not brown. Stir in mushrooms. Cook about 10 minutes or until browned, and liquid has evaporated. Stir in flour. Add whipping cream all at once. Cook and stir until thickened and bubbly.
Remove the skillet from heat. Stir in chives, parsley, lemon juice, salt, and red pepper. Spoon mixture into tart shells. Sprinkle with Parmesan cheese.
Bake in a 350 degree F oven for 10 minutes or until heated through. If you like, garnish with sliced chili pepper and small herb sprigs. Makes 24 appetizers.
Make tart shells and filling the day ahead. Cover and chill filling and tart shells separately. Just before serving, spoon filling into tart shells and bake as above until heated through.