In a medium bowl, whisk together the flour, unsweetened cocoa powder, baking powder, baking soda, salt, and granulated sugar.
Make a well in the center of the flour mixture and add the milk, egg, vanilla, and canola oil. Mix the wet ingredients with the flour mixture until completely blended.
Spray the donut pan with nonstick cooking spray. Add the donut batter to the pan. You should get 6 donuts with this recipe.
Bake donuts in a 325-degree oven for 12 - 14 minutes. A toothpick will come out clean when inserted into the donut.
Remove the pan from the oven and cool slightly on a cooling rack.
Using a butter knife, gently release the donuts from the side of the pan and flip the pan over. Let the chocolate donuts continue to cool on the wire rack.
To make the frosting
In a microwave-safe, small bowl, whisk together the powdered sugar, salt, and unsweetened cocoa powder. Add the milk and vanilla and stir well.
Put the frosting in the microwave for 15 to 20 seconds. Stir. You might want to do this 2 to 3 times.
When frosting is thin enough, dip the top of each donut into the frosting and place them on a wire rack or a piece of parchment paper.
The frosting will hard slightly as it cools.
Notes
**If you prefer, you can add the frosting ingredients to a small saucepan and heat over medium-low heat. **Store these donuts lightly covered. After a couple of days, you might notice the frosting start to weep a bit. But don't worry, I bet they don't last that long.