Slightly Chocolate Coffee Cake

This coffee cake has a rich and crumbly chocolate crust and a fluffy inside with a hint of chocolate and nuttiness. The basic recipe for the batter comes from Rose's Heavenly Cakes, a book with amazing photography and recipes that are as good as they look. But the crust invention and the flavorings are all my own :)
Actually, I was not planning on baking this weekend, but my good friend (also named Masha) who was visiting said: "Masha, cook something sweet." So I did, with lots of help from her, and even more giggles from both of us. As much as I enjoy cooking, doing it with somebody else is infinitely more fun. But alas, I only got a chance to take a picture of the final product.
Is your sweet tooth aching yet? Let's see how it's done!

What you need:
for the crust:
1/2 cup nuts (almonds, walnuts of both)
1/2 cup cocoa (no milk added)
3 Tbsp brown sugar
1/8 spoon cinnamon
1 Tsp butter for the cake pan

for the batter:
3/4 cup almonds
1/2 cup dark chocolate chips
3 large eggs
1.25 cups brown sugar
1 cup sour cream
14 Tbs unsalted butter
1 Tsp vanilla extract
1 Tbsp Fra Angelico
1 Tbsp spiced rum
2 cups all-purpose flour
1.25 tsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1 tube cake pan

How to do it:
0. Preheat oven to 350 degrees Fahrenheit.
1. Cut up butter for the batter into chunks and place into a large mixing bowl to soften.
2. Prepare the cake pan: Put all ingredients (except butter) for the crust into a food processor and chop until a rough-textured flour forms. Smother the cake pan with butter (you can place a 1 Tbsp of butter into the cake pan and put it into the oven for 20 seconds, then spread it around with your fingers so that the walls are evenly covered). Pour the nut/cocoa flour into the buttered pan and carefully shake and turn the pan over the sink until its walls are evenly covered with the flour, which adheres well to the butter. If any flour remains, you can throw it into the batter.
3. Sift the flour, baking soda, baking powder and salt into a clean empty bowl. Chop up nuts and chocolate chips for the batter in a food processor until a rough flour forms and throw into the bowl with the flour. Mix the ingredients in the bowl.
4. When the butter is soft, cream it with a wooden spoon (or a paddle attachment on a stand mixer, which I don't have yet) until it is soft and fluffy.
5. Combine eggs, sugar, rum, vanilla, Fra Angelico and beat on high with a mixer until a liquid foam forms. Add sour cream and beat on low just until incorporated.
6*. Add the egg mixture two tablespoons at a time to the butter mixture, mixing thoroughly in between. Do not add more than two tablespoons at a time, else you will not be able to mix the liquid into the butter. After about half of the egg mixture is incorporated, add flour to the butter mixture in three portions, mixing well in between. Finally, pour the rest of the egg mixture in and mix it in thoroughly. This is your batter.
7. Pour the batter into the prepared cake pan, smooth it with a wooden spoon so that the surface is even. Set in the oven preheated to 350 Fahrenheit and bake for 50 minutes to an hour. Test for readiness by inserting a wooden toothpick into the interior of the cake. If it comes out clean, the cake is done.

8. Enjoy! This dessert is rich, aromatic and flavorful. It's not your everyday cake.

Notes:

* Rose Beranbaum in her book (See Black Chocolate Party Cake in Rose's Heavenly Cakes) describes a different way of incorporating the ingredients, but her instructions are not entirely clear and require a special mixer attachment, so I came up with my own instructions. Though it's possible hers are better, mine certainly work well too.