1. Preheat the oven to 350 degrees F.
2. Grease three-9 inch round cake pans. Line with wax paper and then grease again.
3. Place all of the ingredients, except the boiling water, into a large bowl. Beat for one minute on medium speed.
4. Add the boiling water and continue beating for another minute.
5. Divide the batter evenly among the 3 cake pans. Bake for 20 minutes or until done.
6. While the cake is in the oven, make the Kahlua filling. Boil 2 cups of water over high heat in the bottom part of a double boiler. Place all the ingredients (with only ½ cup of Kahlua) in a large bowl over the double boiler. Stir the mixture continuously until it thickens, about 6-8 minutes. Remove from the heat and let cool.
7. Un-mold the cakes and lay out on 3 separate plates. Pour the remaining ½ cup of Kahlua on top of all three. Let cool for 2-3 hours. When ready to frost, place the first layer on a serving plate, spread with ½ of the Kahlua filling. Top with the second layer and spread with the remaining filling. Top with the third layer and frost with chocolate butter cream frosting.
CHOCOLATE BUTTER CREAM FROSTING (for one cake):
Beat ½ cup softened butter (one stick) in a mixer, add 3 cups powdered sugar, ¼ cup milk, 1/8 cup cocoa, and 1 teaspoon vanilla. Beat until fluffy.