In a microwave or double boiler, melt butter and chocolate; cool for 10 minutes. Combine flour, baking powder, baking soda and salt; set aside. In a mixing bowl beat eggs, sugar, applesauce and vanilla. Stir in chocolate mixture. Add dry ingredients; mix well. Pour into a greased 13-inch x 9-inch x 2-inch pan. Bake at 350°F for 20 to 30 minutes, or until cake tester inserted in center comes out clean. Set aside 1/2 cup marshmallows for glaze. Sprinkle remaining marshmallows over cake. Return to oven for 2 minutes or until marshmallows are softened. In a saucepan, combine sugar, milk and butter. Bring to a boil; boil for 1 1/2 minutes. Remove from the heat; stir in chocolate chips and reserved marshmallows until melted. Quickly drizzle over the cake (glaze will harden as it cools).