Chocolate Sandwich Cookies

1/2 cup butter, softened1 1/4 cups sugar1 egg1 1/4 teaspoons pure vanilla extract2 cups flour 3/4 cup unsweetened cocoa (Nestle preferred) 1/2 cup sweetened cocoa (Ghirardelli preferred), see note1 1/2 teaspoons baking soda 1/2 teaspoon baking powder1 cup milkFilling 3/4 cup butter2 cups powdered sugar 1/2 cup marshmallow creme1 1/2 teaspoons pure vanilla extractHeat oven to 425 degrees.For the cookies: Cream butter and sugar in mixer until light and fluffy. Add egg and vanilla, beat thoroughly.In separate bowl, whisk together flour, cocoas, baking soda and baking powder. Add to butter/sugar mixture alternately with milk, beating until smooth after each addition.Drop by rounded tablespoon onto ungreased cookie sheets 2 inches apart. Bake 8-10 minutes or until tops start to crack and leave no indentation when touched; cool on racks.For filling: Beat together butter, powdered sugar, marshmallow creme and vanilla until light and fluffy. Spread on flat side of one cookie, press flat side of second cookie over filling. Repeat.Serves 24.Editor's note: If you can't find sweetened cocoa, mix 1/4 cup unsweetened cocoa with 1/4 cup sugar.Nutrition values per cookie: 236 calories, 10 g fat (7 g saturated), 36 g carbohydrates, 1 g fiber, 2 g protein, 34 mg cholesterol, 120 mg sodium.