Preheat the oven to 350°F. Spray a donut pan with nonstick cooking spray. Set it aside.
Add all dry ingredients to a medium bowl and mix together: all purpose flour, brown sugar, cocoa powder, baking powder, baking soda, and salt.
In a large bowl, combine the wet ingredients: milk, sour cream, egg, vegetable oil and vanilla extract. Whisk together.
Add the flour mixture to the wet ingredients and mix until just combined. Do not overmix.
Add batter to a sandwich bag and snip off a corner. Pour into the donut cups halfway full (it's better to under fill than over fill as the donuts will rise while baking). Bake for 10-11 minutes, or until a toothpick comes out clean when poked in the center.
Transfer donuts to a wire rack to cool compleltely. Cut out the inside holes of any donuts that need it using a sharp knife.
While donuts are cooling, mix together the glaze. Add the powdered icing sugar, milk and vanilla extract to a bowl. Mix together.
Dip the top and bottom of each donut into the glaze. Place back on the wire rack for glaze to harden. Tip: Place a sheet of parchment paper underneath to catch any glaze drips.
Recipe Notes:
How To Store
COUNTERTOP – Donuts can be stored in an airtight container or wrapped in plastic for one day at most. After that, the moisture will evaporate and the donuts will turn stale.
REFRIGERATE – You can store these for up to 3-4 days in a sealed container.