Grease or line the wells of a standard 12-cup muffin tin and set it aside.
To make the batter in a blender, see the Recipe Notes.
Place the oat flour, baking powder, baking soda, salt, and pumpkin pie spice into a large mixing bowl, and whisk to combine well.
In a medium-size mixing bowl, place the pumpkin puree, sour cream, eggs, vanilla, and sugar, and whisk well until very smooth.
Pour the wet mixture into the large mixing bowl of dry ingredients, and mix until just combined.
Add about 4 of the 5 ounces of the chocolate chips, and mix to distribute the chips throughout the batter.
Cover the mixing bowl and let the raw muffin mixture sit for at least 20 minutes, and up to 1 hour or more. The batter will thicken as it sits.
Preheat your oven to 350°F.
Divide the batter evenly among the prepared wells of the muffin tin. The wells should be completely full. Sprinkle the tops evenly with the remaining chocolate chips.
Place the muffin tin in the center of the preheated oven and bake for about 25 minutes, or until the tops of the muffins spring back when pressed gently in the center.
Remove from the oven and allow to cool in the tin for 10 minutes before transferring to a wire rack to cool completely.
Video
Notes
To make the batter in a blender.If you're beginning with old fashioned oats instead of oat flour, blend 3 cups of oats into a fine powder first, then remove from the blender. Place the oat flour in a large mixing bowl, and whisk in the baking powder, baking soda, salt, and pumpkin spice. Place the pumpkin puree, sour cream, eggs, vanilla and sugar in the blender, and blend until smooth. Pour the wet ingredients into the dry, and proceed with the recipe as written, starting with step 5.