Preheat oven to 300 degrees. Spray a mini bundt cake can with vegetable oil.
Whisk together flour, sugar, baking soda, salt and cocoa in a small bowl.
Cream together egg, butter, sour cream, vanilla and coffee. Add to dry ingredients.
Add batter by the teaspoonful to each compartment up to the hole. Bake at 300 degrees for about 20 to 30 minutes until an inserted toothpick comes out clean. Cool cakes in pan on rack for several minutes before removing.