Sift flour once, measure, add baking powder, salt and soda, and sift together three times. Cream butter thoroughly, add sugar gradually, and cream together until light and fluffy. Add egg and egg yolks, one at a time, beating well after each. Add chocolate and blend. Add flour, alternately with milk, a small amount at a time, beating after each addition until smooth. Add vanilla, then add boiling water, beating quickly and thoroughly.
Bake in greased pan 12x8x2 inches, in moderate oven (325 degrees F.) 50 minutes, or until done. Spread Peanut Cream Frosting on top of cake.