Preheat the oven to 350ºF. Spray a donut pan with non-stick cooking spray then use a paper towel to evenly coat the entire donut well.
In a smaller bowl, combine the flour, cocoa powder, granulated sugar, baking powder and salt, mix until combined. Set aside.
In a mixing bowl combine the milk, egg, vanilla extract and vegetable oil, use a whisk or spatula to beat. Gradually add the flour mixture, mixing by hand with a spatula just until combined.
Transfer the batter to a piping bag fit with a round piping tip, or transfer the batter to a ziplock bag, then cut off one corner and pipe the batter evenly into the donut wells. Use a small spatula to smooth the tops of the batter if the batter is uneven.
Bake for 10-13 minutes or until a toothpick inserted in the center of a donut comes out clean. Allow the donuts to cool for 10 minutes in the donut pan. Then turn the donut pan upside down and hit the pan against a counter a few times to release the donuts. Allow them to cool completely before dipping.
Place chocolate chips and oil in a microwave safe bowl, microwave 1 minute on 50% power, then stir. Return to the microwave and continue to heat for 30 seconds at a time on 50% power until the chocolate is melted. Stir the chocolate until smooth. Allow the chocolate to cool for a few minutes before dipping. Dip the donut into the chocolate, allowing the excess to fall off into the chocolate bowl. Add sprinkles if desired. Allow the glaze to harden or enjoy right away.