Beat butter, shortening, and salt together with an electric whisk sugar rise enough to beat the cream until light and fluffy egg, one egg white, smash together and beat until the egg.
Beat the shortening, salt and butter together with an electric beater or just foo: foo, put more sugar and cream until it hit a white egg the fist place individually bubble hit together until all the eggs.
Beat butter white butter and salt together with the egg mixture and electric sugar beat until fluffy. Break the eggs one by one is a white cream foam, to beat eggs until the end.