For the bars, preheat the oven to 350 degrees Fahrenheit and grease a 9x9x2 inch baking pan. In a large mixer bowl, beat butter and sugar on medium speed until light and fluffy. Add egg, malted milk powder, milk, and vanilla. Beat until thoroughly combined.

In a small bowl stir together flour, baking powder and salt. With mixer on low speed, gradually add flour mixture to the sugar mixture, beating until thoroughly combined.

Fold in 1 1/4 c. malted milk balls. Spread mixture into a greased 9x9x2 inch baking pan. Bake for approximately 20 minutes or just until a toothpick inserted near the center comes out mostly clean (moist crumbs are good).

Cool bars on a wire rack.

For the frosting, in a mixer bowl, combine powdered sugar and cocoa powder. Add butter, boiling water and vanilla. Beat with mixer on low speed until combined. Allow to cool slightly, then spread over bars and sprinkle with remaining 1/3 c. malted milk balls.