Preheat your oven to 350F and grease a standard donut pan very well, including the centers of the donut pan.
Add all donut ingredients to a medium bowl and stir until well combined.
Divide batter evenly between 10 donut cups, filling each about three-quarters full, using a scant ΒΌ cup batter per donut.
Bake for 18 to 20 minutes, or until a cake tester inserted into the center of each donut comes out clean.
Remove from the oven and let donuts cool in the pan for 5 minutes. Use a paring knife to loosen the edges of the donuts as needed and transfer to a wire rack to cool completely.
Stir together powdered sugar, cocoa powder, and milk in a small bowl until icing is smooth.
Dip each cooled donut into the icing and top with crushed candy canes. Let sit for a few minutes (at least) before serving so the icing sets.