Cream together the butter, sugar, and vanilla until fluffy; beat in eggs. Blend in cooled chocolate. Sift together flour, malted milk powder, baking powder, and salt. Add dry ingredients to the creamed mixture, stirring to blend well. Fold in chopped pecans or walnuts. Spread in a greased and floured 8-inch square baking pan. Bake at 350° for 20 to 25 minutes. Cool and frost with Chocolate Malt Frosting.
For frosting, cream 2 tablespoons butter with 1/4 cup chocolate flavored malted milk powder and salt. Slowly beat in confectioners' sugar and just enough half-and-half to make frosting a good spreading consistency.
Makes 16 malted milk bars.