Line bottoms of 3 9” cake pans with wax paper, grease sides.
Microwave chocolate and water 1 ½ - 2 minutes until chocolate is almost melted, stirring after each minute.
Stir until chocolate is completely melted.
Mix flour, baking soda and salt, set aside.
Beat butter and sugar in large bowl until light and fluffy.
Add egg yolks one at a time, beating well after each addition.
Stir in chocolate mixture and vanilla.
Add flour mixture alternately with buttermilk, beating until well blended after each addition.
Beat egg whites in another large bowl with electric mixer on high speed until stiff peaks form.
Gently stir into butter, pour evenly into prepared pans.
Bake at 350°for 30 minutes, immediately run spatula between cakes and sides of pans.
Cool 15 minutes, remove cake layers from pans. Remove wax paper. Cool completely on wire racks.
Spread coconut-pecan filling and frosting between layers and on top of cake.