Step 1

In a saucepan, melt butter. Remove from the heat. Stir in cocoa; cool. In a large bowl, beat eggs and sugar until blended. Combine flour, baking powder and salt; gradually add to egg mixture. Stir in vanilla and the cooled chocolate mixture until well blended.

Step 2

Spread into a greased 13x9-in. baking pan. Bake at 350° until a toothpick inserted in the center comes out clean, 25-28 minutes (do not overbake). Cool on a wire rack.

Step 3

For frosting, in a large bowl, cream butter and confectioners' sugar until light and fluffy, 5-7 minutes. Beat in cocoa and vanilla. Add enough milk for the frosting to achieve spreading consistency. Spread over brownies. Cut into bars.