Preheat oven to 375 degrees.
In a medium mixing bowl, combine the flour, sugar, grated chocolate, baking powder, baking soda, and salt.
In a small bowl, beat together the vanilla, egg, sour cream, milk, and oil.
Stir the wet ingredients into the dry until just combined.
Spoon in a greased doughnut pan.
Bake for 8 minutes or until the tops spring back when you touch them.
Let the donuts cool completely in the pan before glazing.