Preheat oven to 325 degrees. Lightly grease a 13 X 9 baking pan and set aside. In a medium bowl, combine flour, malted milk powder, and salt, then set aside. In a medium saucepan, combine butter and chocolate, then heat and stir over low heat until chocolate melts. Remove from heat and stir in sugar. Using a wooden spoon, beat in eggs, one at a time. Add vanilla. Stir in flour mixture, walnuts, and half of the crushed malted milk balls. Spread in prepared pan. Bake for 35 minutes. Cool in pan on a wire rack. Cut into bars. To package, place remaining crushed malted milk balls in a small plastic bag and include the instructions, "use a small amount of canned frosting to 'glue' malted milk ball pieces atop bars".