Combine the flour, sugar, cocoa powder, and baking soda together in a bowl.
In another bowl, combine the egg, sour cream, milk and vegetable oil.
Add the wet ingredients to the dry ingredients and combine.
Using a plastic pastry bag, fill the donut pan with the batter and bake in a 375 degree preheated oven until a toothpick comes out clean; about 8 to 10 minutes.
Remove the donuts from the pan and allow to cool on a baking rack before drizzling the glaze on top.
How to Add the Glaze:
Combine all the ingredients for the glaze in a mixing bowl.
Using a spoon, drizzle the glaze on top of the cooled donuts.
Notes
Wait about 10 minutes or so before you actually eat the donuts. Letting them rest after you pour the glaze on helps set the glaze so the donuts aren’t too wet.