Melt bars and butter, set aside. Beat eggs & sugar--add flour & soda alternately with buttermilk. Add melted bars & butter to flour mixture and combine thoroughly. Pour into greased angel food cake pan. Bake at 325 degrees for 1 hour 10 minutes. Cool on wire rack about 10 minutes before removing from pan. You may have to run a knife around edges of the pan to release cake onto a rack.