Prepare the Coconut-Macaroon Filling.

In a small bowl, beat egg white until soft peaks form.

Gradually add sugar to the egg white; beat until stiff peaks form.

By hand, stir in coconut, flour and vanilla, blending well.

Set the Coconut-Macaroon Filling aside.

Preheat oven to 350°F (175°C).

Grease and flour a 12-cup Bundt pan.

In a large mixing bowl, combine sifted flour, sugar, cocoa, salt, baking soda, vanilla, cold water, sour cream, eggs, egg yolk, and shortening.

Blend at low speed until moistened.

Beat at medium speed for 3 minutes.

Pour the chocolate batter into the prepared Bundt pan.

Drop teaspoonfuls of coconut filling over the chocolate batter.

Bake for 55-65 minutes, or until a cake tester comes out clean.

Cool in the pan for 10-15 minutes.

Turn the cake out onto a serving plate or rack to cool completely.

Top with vanilla or chocolate glaze (optional).