This was sent to me recently and it might be what you are looking for.

Chocolate Macaroon Tunnel Cake

This cake recipe is the result of a discontinued, but
wonderful box mix. It is a chocolate cake that slices to reveal a beautiful white coconut center. The vanilla glaze can easily be made into chocolate by adding 2
tablespoons of cocoa powder.

1/2 cup shortening
1 3/4 cups white sugar
1 egg yolk
2 teaspoons vanilla extract
4 eggs
2 cups sifted all-purpose flour
1/2 cup unsweetened cocoa powder
1 teaspoon baking soda
1 teaspoon salt
3/4 cup cold water
1/2 cup sour cream

Coconut Macaroon Filling:
1 egg white
1/4 cup white sugar
1 cup flaked coconut
1 tablespoon all-purpose flour
1 teaspoon vanilla extract

Vanilla Glaze:
2 cups sifted confectioners' sugar
1 tablespoon butter, softened
1 teaspoon vanilla extract
2 tablespoons milk, or as needed

Preheat the oven to 350 degrees F (175 degrees C).
Grease and flour a 10 inch Bundt pan.
In a large bowl, blend together the shortening, 1 3/4
cups white sugar, egg yolk and vanilla until smooth. Beat
in eggs one at a time using an electric mixer. Combine 2
cups flour, cocoa, baking soda and salt; stir into the egg
mixture alternately with the sour cream and water. Pour batter into the prepared Bundt pan.

In a separate bowl with clean beaters, whip the egg
white until soft peaks form. Gradually sprinkle in 1/4 cup
white sugar while continuing to whip to firm peaks. Fold in
the coconut, 1 tablespoon of flour and 1 teaspoon of
vanilla by hand using a spatula or wooden spoon. Drop this
mixture by teaspoonfuls over the chocolate batter in the pan.

Be careful not to let the filling touch the sides of the pan.

Bake for 55 to 65 minutes in the preheated oven, or
until a knife inserted into the cake comes out clean. Cool
for 15 minutes in the pan, then invert onto a wire rack to
allow the cake to cool completely. Remove cake from pan, and drizzle with vanilla glaze.

To make vanilla glaze, mix together the confectioners'
sugar, butter and milk in a small bowl, gradually adding milk until the mixture is thick but pourable. Drizzle over
cooled cake.