Combine flour and baking soda; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in pecans and coconut. Beat egg whites at medium speed until stiff peaks form; fold one-third of egg whites into batter. Gently fold in remaining beaten egg whites just until blended. Spoon batter into 3 greased and floured 9-inch cake pans.

Bake 25 minutes or until a toothpick inserted comes out clean. Cool in pans on wire racks 10 minutes; remove from pans, and cool completely on wire racks. Spread Pecan Pie Filling between layers. Spread Cream Cheese Frosting on top and sides of cake. Sprinkle top and sides with toasted pecans and toasted coconut.

Pecan Pie Filling  Whisk together first 6 ingredients in a heavy 3-qt. saucepan until smooth. Bring mixture to a boil over medium heat, whisking constantly; boil 1 minute or until thickened. Remove from heat; whisk in butter and vanilla. Place a sheet of wax paper directly on surface of mixture to prevent a film from forming, and chill 4 hours.

Cream Cheese Frosting  Beat butter and cream cheese at medium speed with an electric mixer until creamy. Gradually add powdered sugar, beating at low speed until blended; stir in vanilla.