Preheat oven to 350 degrees F. Grease a 15x10x1-inch baking pan; set aside. In a very large bowl, combine flour, sugar, malted milk powder, baking soda, and salt; set aside.
In a medium saucepan, combine butter, cocoa powder, and 1 cup water. Bring mixture just to boiling, stirring constantly. Remove from heat. Add the cocoa mixture to flour mixture and whisk or stir vigorously until thoroughly combined. Add eggs, buttermilk, and vanilla. Whisk or stir until combined (batter will be thin). Pour batter into the prepared pan.
Bake about 25 minutes or until a wooden toothpick inserted in the center comes out clean. Place cake in pan on a wire rack.
Sprinkle malted milk balls evenly over warm cake. Drizzle warm Chocolate-Buttermilk Frosting over the malted milk balls. Cool thoroughly before cutting. Serve cake same day or cover and refrigerate up to 24 hours for longer storage. Makes 24 servings.
In a medium saucepan, combine butter or margarine, cocoa powder, and buttermilk or milk. Bring to boiling. Remove from heat. Add powdered sugar and vanilla. Beat until smooth. Let frosting cool for 15 minutes or until slightly thickened, stirring occasionally, before drizzling over cake.