Beat butter and shortening at medium speed with an electric mixer 2 minutes or until creamy. Gradually add brown and granulated sugars, beating until light and fluffy. Add eggs, 1 at a time, beating just until blended.
Combine flour, baking powder, and salt. Add to butter mixture alternately with milk, beginning and ending with dry ingredients. Stir in vanilla and toffee bits.
Spoon batter into 2 greased and floured Bundtlette pans, filling each cup 2/3 full. Sprinkle with chopped nougat bars, pressing candy gently into batter.
Bake at 325° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans to cool on wire racks. Sprinkle with powdered sugar before serving.