Preheat oven to 325 degrees F. Line a 15x10x1-inch baking pan with foil, extending the foil over edges of pan. Grease foil; set pan aside.
In a large saucepan heat and stir butter and unsweetened chocolate over low heat until smooth. Whisk in eggs, sugar, and vanilla.
In a small bowl combine flour, malted-milk powder, and salt. Add flour mixture to chocolate mixture, stirring to combine. Stir in chopped chocolate malted-milk balls. Spread batter in the prepared pan.
Bake in the preheated oven about 30 minutes or until set. Cool in pan on a wire rack. Using the edges of the foil, lift brownies out of pan. Using a 2-inch round cutter, cut brownies into rounds.
Pipe or spread Chocolate Malted-Milk Filling on the top center of each brownie round. Place half of a chocolate malted-milk ball on the chocolate filling on each brownie round.
Chocolate Malted Milk Filling
In a medium microwave-safe bowl combine milk chocolate pieces and whipping cream. Microwave, uncovered, on 100 percent power (high) for 1 minute. Whisk until chocolate melts and mixture is smooth. Stir in chocolate malted-milk powder. Cover; chill for 30 minutes, stirring every 10 minutes. Beat with an electric mixer on medium-high speed until filling is fluffy, being careful not to overbeat. (Or instead of chilling chocolate filling, place the bowl in a larger bowl filled with ice cubes. Beat filling with an electric mixer on medium-high speed until fluffy, being careful not to overbeat.)