Melt chocolate in boiling water; cool. Cream together butter and sugar. Beat in egg yolks, one at a time, beating well after each addition. Add melted chocolate and vanilla. Sift together the flour, baking powder, and salt. Add to chocolate mixture, alternating with the buttermilk. Do not over beat. Fold in beaten egg whites, gently. Stir in nuts and coconut. Divid evenly into three generously greased and lightly floured cake pans. Bake in 350~ oven for 30-45 minutes..until lightly browned and center springs back at your touch. Cool, and frost with icing. Coconut Frosting: Cook sugar, water, and Karo until it reaches soft ball stage. Pour syrup into egg whites and beat until stiff. Add salt and vanilla. Spread between layers and on top and sides of cake. Sprinkle icing with coconut as thickly as you like.