In a stand mixer, beat together 10 tablespoons butter and brown sugar on medium speed for 3 minutes. Add pumpkin puree and eggs and mix for another 1 minute.
In a separate bowl, stir together flour, baking powder, baking soda, salt, 1 and ½ teaspoons cinnamon, and nutmeg. Slowly incorporate the dry ingredients into the pumpkin mixer on low speed. Add milk and continue to mix until all ingredients are evenly distributed.
Divide batter into a greased mini muffin pan. Bake for 12-14 minutes.
Transfer muffins to wire cooling rack and allow to cool for 15 minutes.
Meanwhile, melt 8 tablespoons of butter in a bowl. Combine sugar and 2 and ½ teaspoons cinnamon and spread across a plate.
Dunk doughnut holes in butter and coat in cinnamon sugar. Return to baking rack to cool.
Recipe by Rachel Schultz at https://rachelschultz.com/2016/08/23/pumpkin-donut-muffins/