Preheat the oven to 425°F. Line a 12-cup muffin pan with 6 muffin liners. Set aside. You can use two muffin pans, or just reuse the pan.
In a mixing bowl, sift the flour. Add in the brown sugar, baking powder, baking soda, cinnamon, salt, nutmeg, and pumpkin pie spice.
2 cups All-purpose flour, 3/4 cup Brown sugar, 1 TBSP Baking powder, 1/4 tsp Baking soda, 2 tsp Ground cinnamon, 1/2 tsp Salt, 1/4 tsp Ground nutmeg, 1 tsp Pumpkin pie spice
In a separate bowl, Mix the oil, buttermilk, egg, pumpkin puree, vanilla, and sour cream. Pour the wet ingredients into the dry. Mix until combined. Fold in the mini chocolate chips.
1/2 cup Buttermilk, 1 Large egg, 1 cup Pumpkin puree, 1 tsp Pure vanilla extract, 1/4 cup Sour cream, 1 cup Mini chocolate chips, 1/2 cup Oil
Scoop the muffin batter and fill the liners all the way to the top. Use all of the batter. Top the muffins with extra chocolate chips.
Bake for 10 minutes. Then, turn the oven to 350°F. Bake for another 8-10 minutes. They are done baking when a toothpick inserted comes out clean.
Let the muffins sit for 10 minutes before transferring to a cooling rack. Let the muffins cool slightly before enjoying.