PREHEAT oven to 350º.
BUTTER and lightly flour three 9 inch round cake pans.
SIFT SWANS DOWN Cake Flour, then lightly spoon into measuring cup for 2¾ cups.
COMBINE chocolate and boiling water; stir until chocolate melts. Set aside.
CREAM butter; gradually add sugar, beating well at medium speed of an electric mixer. Add eggs, one at a time, beating well after each addition.
ADD salt to already measured SWANS DOWN Cake Flour.
DISSOLVE baking soda in buttermilk.
ADD flour mixture to creamed mixture alternately with buttermilk, beginning and ending with flour mixture. Stir in chocolate and vanilla.
POUR batter into prepared pans. Bake at 350 for 30 to 35 minutes; remove from pans once cooled and place on wire racks to cool completely.
SPREAD Butter Filling between layers; spread Chocolate Frosting on top and sides of cake. Optional – press chopped pecans into frosting on sides of cake and place pecan halves on top.