It might sound weird, but black beans and chocolate actually make a very tempting combo and give a wonderfully dense texture (hence the name mud cake) to a cake.
Just the names of the recipes make you salivate: Mississippi - Mud Cupcakes, Maple Pecan Chiffon Cake with Brown Butter Icing, Old Vermont Burnt Sugar Cake with Maple Cream Cheese Frosting... I mean, seriously, best names ever.