Grease and lightly flour three 9x1-1/2-inch round cake pans. Set the pans aside.
In a mixing bowl, mix flour, soda, and salt.
In saucepan, heat, stir chocolate and water until chocolate melts. Remove from heat; cool.
In a large mixing bowl, beat butter with an electric mixer for 30 seconds. Beat in the sugar until fluffy. Beat in egg yolks, one at a time, beating well after each. Beat in chocolate and vanilla.
Alternately add the flour mixture and the buttermilk, beating on low speed after each addition. Wash the beaters thoroughly.
In medium bowl, beat egg whites on high until stiff peaks form. Fold whites into batter. Divide the batter among the prepared cake pans.
Bake in a 350 degree F oven for 30 to 35 minutes or until a toothpick inserted into the centers comes out clean. Cool 10 minutes in pans on wire racks. Remove layers from pans; cool.
Prepare Coconut-Pecan Topping. Place a cake layer on serving plate and spread with one-third of the topping. Top with second cake layer and one-third of the topping. Top with last cake layer and remaining topping. Chill until ready to serve.
In a saucepan, combine evaporated milk, sugar, egg yolks, and butter or margarine. Cook and stir until slightly thickened and mixture just bubbles. Stir in vanilla, flaked coconut, and chopped pecans. Cool.