Combine butter, sugar, flour, cocoa, baking powder, eggs, milk, and 1 1/2 teaspoon of vanilla; beat well. Stir in nuts. Spread into a greased and floured 13 x 9 inch pan. Bake 40 minutes.
Just before brownies are done, melt chips in a saucepan with 1 1/2 teaspoon vanilla and condensed milk. Spread fudge mixture over hot brownies. Cool. Chill and cut into bars. (The icing cools very quickly, so if you want to add swirls or fork lines to the top of the brownies work quickly! :).