Preheat the oven to 350°. Spray two 6 count donut pans with cooking spray. Alternatively, you can just use one pan and bake one batch at a time.
Mix flour, sugar, baking soda, baking powder and salt together in a large bowl.
Make a well in the center of the dry ingredients and add pumpkin, milk, vanilla, egg and oil.
With a mixing spoon or heavy duty scraper, mix everything together just until blended. Fold in the chocolate chips.
Spoon about two generous tablespoons of batter into each donut ring and spread evenly – batter should come just about to the top.
Bake donuts for 12 minutes or until a they spring back when touched.
Flip from the pan while still warm, then prepare glaze and drizzle over doughnuts.
To make the glaze, combine warm melted butter and cocoa powder in a bowl and stir until smooth.
Add milk and stir until smooth, then add powdered sugar about ½ cup at a time, mixing until smooth. Add vanilla. Add more milk only if needed. Glaze sets as it cools, so work quickly. If glaze starts to set, you can warm it for a few seconds in the microwave.
Notes
This batter makes enough for 12 donuts, but most standard donut pans only have 6 cavities. You can use two donut pans or make one pan at a time (batter sits okay). For the flour, it's best to weigh it. If measuring by volume only, be sure to stir and aerate it then spoon it into the cup carefully.