Preheat oven to 350 degrees. Spray pans with vegetable oil.
In a large bowl cream butter and sugar with electric mixer. until light and fluffy. Add eggs one at a time and vanilla mix well.
Combine flour, baking powder, and salt. Add to butter mixture alternately with milk, mix well after each addition. Continue beating 1 minute. Divide batter in half. Stir melted chocolate into half the batter. MIX WELL.
Place Dividing Batter Ring into one prepared pan. Follow instructions for filling sections. ( For convenient filling, place batter in 2 disposable decorating bags )one for yellow and one for chocolate.
Bake layers 30 to 35 minutes or until toothpick inserted in center comes out clean Cool in pan 10 minutes. Remove from pan and cool completely
Assemble cake following directions. Ice entire cake with chocolate icing. Serves 20
NOTE: If you don't have a set of checkerboard cake pans. You can get them at ( www.wilton.com )