Preheat oven to 325 degrees F (160 degrees C).
Melt the Unsalted Butter (3 tablespoon).
Whisk All-Purpose Flour (1 cup), Unsweetened Cocoa Powder (1/4 cup), Baking Powder (1/2 teaspoon) and Salt (1/4 teaspoon) together.
In a separate bowl, combine Milk (1/2 cup), Dark Brown Sugar (1/2 cup), Egg (1), melted unsalted butter and Vanilla Extract (1 teaspoon).
Pour flour mixture into milk mixture and mix until incorporated.
Grease donut pan and fill 2/3 full, and bake for 13 minutes.
Let cool for a minute in pan and then turn out onto a wire rack. Dip into Chocolate Icing (to taste) and Sprinkles (to taste).