So I made some pretty sweet cookies for my friends from the internet. I can't recall the precise recipe, I will post it when I get home, but the basic premise was, mix up cookies dough, but before adding the flour, split the soft stuff (1/2 cup butter 1/2 cup shortening 1 cup packed brown sugar 2 eggs dash vanilla 1 tsp(???) baking powder) in half, and give one half white flour (1.5 cups?) and a half cup of cocoa powder, and the other a cup and a half rye flour (1.5 cups) and a cup of chocolate chips.
Place the chocolate cookie dough between two pieces of wax paper, roll it out. Place the chocolate chip dough between two pieces and flatten. Place the layers on top of each, and roll it up. If you want, flatten again and fold to marble, or, if you've rolled it long side up, you may be able to just slice spiral round cookies off of the roll.