Thaw crawfish or shrimp, if frozen. In a 3-quart saucepan melt butter or margarine. Add onion, green pepper, celery, green onions, parsley, and garlic. Cook and stir about 10 minutes or until vegetables are very tender.
Stir in flour until blended. Stir in chicken broth, tomato sauce, salt, red pepper, and black pepper. Bring to boiling. Reduce heat. Cover and simmer mixture for 20 to 25 minutes.
Combine cornstarch and water. Stir into skillet. Add crawfish. Cook and stir until thickened and bubbly. Cook 2 minutes more. Remove from heat.
Prepare pastry. Roll out half of the pastry to 1/8-inch thickness. Cut 2 bottom crusts to fit 3 inches wider than a 10-ounce casserole, ease 1 crust into each of 2 casseroles. Trim even with edge. Cut 2 top crusts 1 inch wider than casseroles. Pour 1 cup filling into each pastry-lined casserole. Top each with a pastry round. Fold extra pastry under bottom crust. Flute edge. Repeat to make 2 more pies. Cut decorative trimmings from pastry scraps and arrange on pies, if desired. Brush crusts with milk. Bake in a 425 degree F oven for 20 to 25 minutes. Makes 4 servings.