COMBINE flour, baking powder and salt in a small bowl. Beat sugar, butter, eggs, Choco Bake and vanilla extract in a small mixing bowl until creamy. Gradually beat in flour mixture. Stir in nuts. Spread into a greased 8-inch-square baking pan.
BAKE in preheated 350° F oven for 25 to 30 minutes or until wooden pick inserted in center comes out still slightly sticky. Cool completely in pan on wire rack. Spread with Fudge Frosting.
FOR FUDGE FROSTING:
BEAT butter, Choco Bake, milk and vanilla extract in a small mixing bowl until well blended. Gradually beat in powdered sugar until creamy.