Preheat the oven to 350 degrees. Line the bottom of a 9-inch tube cake pan with paper and lightly grease the sides.
Combine the egg white and dash of salt in a small bowl; beat until foamy. Add ¼ cup of the sugar, a little at a time, beating at high speed until stiff peaks form. Blend in 2 tablespoons flour and the coconut.
Melt the chocolate in ¼ cup water over very low heat, stirring until blended. Cool thoroughly. Meanwhile, measure the sifted flour, baking soda, salt and baking powder; sift together. Cream the butter and 1 cup sugar. Then, add the eggs, one at a time, beating well after each addition. Blend in the vanilla. Combine the sour cream and the cooled chocolate, blending well. Add to the butter mixture alternately with the flour mixture, mixing well after each addition.
Pour about 2 cups of the cake batter into the prepared pan. Sprinkle with about ½ cup of the coconut mixture. Top with another 2 cups of the batter and ½ cup of the coconut mixture; then with remaining batter and coconut mixture. Bake for 50 to 55 minutes. Cool in the pan on a wire cake rack for 15 minutes; then remove the sides of the pan, leaving the tube in the cake. If the sides of the pan are not removable, cool the cake thoroughly in the pan as the cake is very tender. Spread with glaze and top with more coconut, if desired.
Source: Baker’s Chocolate and Coconut Favorites, General Foods Kitchen, 1962