Heat oven to 350°F.

Cover bottoms of 3 (9-inch) round pans with parchment; spray sides with cooking spray. Microwave chocolate and water in large microwaveable bowl on HIGH 1-1/2 to 2 min. or until chocolate is almost melted, stirring after 1 min. Stir until chocolate is completely melted.

Beat egg whites in small bowl with mixer on high speed until stiff peaks form; set aside. Combine flour, baking soda and salt. Beat butter and sugar in large bowl with mixer until light and fluffy. Add egg yolks, 1 at a time, beating well after each. Blend in melted chocolate and vanilla. Add flour mixture alternately with buttermilk, beating until well blended after each addition.

Add egg whites; stir gently until well blended. Pour into prepared pans.

Bake 30 min. or until toothpick inserted in centers comes out clean. Immediately run small spatula around cakes in pans. Cool cakes in pans 15 min. Remove from pans to wire racks; cool completely.

Prepare Coconut-Pecan Filling and Frosting http://www.kraftrecipes.com/recipes/coconut-pecan-filling-frosting-51053.aspx ; spread between cake layers and onto top of cake.