Using a mixer, beat eggs, vanilla, salt, sugar, butter, baking powder, milk. Gradually add cake flour and beat until smooth. Pour on a greased jelly roll pan (flat pan 15 1/2"x 10 1/2" x 1 1/8"). Looks like a cookie sheet but with sides. Bake at 350 degrees for 15-20 minutes. Spread peanut butter on cake while still warm.
Cool the cake. Melt the chocolate bar and spread over the top with a knife. Cut and eat.