In a small bowl combine cocoa and water, stir until smooth.
Set aside to cool.
Heat oven to 350 degrees.
Grease 3 round pans, 9x1&1/2 inches; line bottoms with wax paper.
In a large mixer bowl cream the butter.
Add sugar and vanilla; beat until light and fluffy.
Add eggs, one at a time, beating well after each addition.
Combine flour, baking soda and salt; add alternately with chocolate mixture and buttermilk to creamed mixture.
Mix only until smooth.
Pour batter into prepared pans.
Bake 25 to 30 minutes or until top springs back when touched lightly in center.
Cool 5 minutes; remove from pans and peel off paper.
Prepare Coconut Pecan Frosting.
Spread frosting between layers and over top.
Garnish with pecan halves, if desired.
Coconut Pecan Frosting
In a heavy 2-quart saucepan combine sweetened condensed milk, egg yolks and butter.
Cook, stirring constantly, over medium heat until mixture is thickened and bubbly, about 10 minutes.
Remove from heat and stir in vanilla, coconut and pecans. Cool about 15 minutes.
Yields about 2&3/4 cups frosting.