Preheat oven to 425° Fahrenheit. Lightly grease donut pan with cooking spray and set aside.
In large bowl, whisk together flour, cocoa powder, sugar, brown sugar, and baking powder until ingredients are thoroughly incorporated.
In small bowl, whisk together eggs, milk, melted butter, and vanilla extract until ingredients are fully combined.
Slowly pour egg mixture into flour mixture, whisking constantly until all ingredients are combined to form donut batter.
Carefully spoon donut batter into greased donut pan, making sure molds are filled equally and batter is evenly divided. Place filled donut pan in preheated oven and bake 7 to 9 minutes, or until toothpick inserted into one donut comes out clean or with very few crumbs.
Remove donuts from oven and transfer to a wire cooling rack to cool completely. Remove baked donuts from oven and carefully transfer from donut pan to wire cooling rack. Let
Once donuts are completely cool, prepare chocolate icing by whisking together all icing ingredients in large bowl until icing is completely smooth. Drizzle prepared icing over cooled donuts, or dip top half of donuts in icing directly. Top with sprinkles if desired and serve.