Preheat oven to 350 degrees. Spray a mini muffin tin with non-stick cooking spray.
In the bowl of a stand mixer, beat together 1/2 cup of butter, 1/2 cup white sugar, and brown sugar until light and fluffy. Beat in the egg, vanilla, and pumpkin until well combined.
Gradually stir in the flour, baking soda, 2 teaspoons of cinnamon and nutmeg.
Fill the muffin wells 2/3 full. Bake for 17 minutes or until a toothpick inserted in the center of a muffin comes out mostly clean. Do not overbake these as you're looking for a fudgy center.
Let cool for 10 minutes before removing the muffins from the tin.
Melt the remaining 1/2 cup of butter in a small bowl.
Stir together the remaining 1/2 cup of sugar and teaspoon of cinnamon and place in a second small bowl.
Dunk each muffin in the butter and then roll in the cinnamon sugar mixture to coat.