Grease two 23 cm layer cake pans or one 9 x dozen pan. Preheat oven to 325 deg f. Combine candy bars and 1 cup butter in a double boiler and melt over hot, but not boiling water, until melted. Set aside. Cream together the remaining butter and sugar, until light and creamy. Add eggs, one at at time, beating well between each addition. Dissolve soda in buttermilk and add to creamed mixture, alternately with flour. Add melted candy and blend until smooth. Spoon batter into prepared pan(s).Bake for 50 to 60 minutes in 9 x dozen pan or 40 to 50 minutes in layer pans.Cake should spring back when lightly touched. Frost as desired.