Beat 3 eggs in 2-quart saucepan with whisk. Stir in brown sugar, half & half and 1/2 cup butter. Cook over medium heat, stirring constantly, 10-15 minutes or until thickened and bubbly. Remove from heat. Stir in coconut, pecans and 2 teaspoons vanilla. Cool completely at least 1 hour.
Heat oven to 350°F.
Combine chocolate and water in 1-quart saucepan. Cook over low heat, stirring occasionally, 6-7 minutes or until chocolate is melted; cool 10 minutes.
Grease and lightly flour 2 (8- or 9-inch) round baking pans; set aside.
Combine flour, baking soda and salt in medium bowl; set aside.
Beat sugar and 1/2 cup butter on medium speed in bowl until creamy. Add 2 eggs and 1 teaspoon vanilla; beat until well mixed. Add chocolate mixture; beat until well mixed. Add flour mixture and buttermilk alternately to chocolate mixture, beating well after each addition, until well mixed. Pour batter into prepared pans.
Bake 33-40 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes. Remove from pans. Cool completely.
Spread frosting over top of each cake; stack layers. Frost side of cake, if desired.
*Substitute 1 tablespoon vinegar or lemon juice plus enough milk to equal 1 cup. Let stand 5 minutes.