Preheat oven to 350 degrees.
In a food processor, shred 6 carrots. (more or less, you need to cups worth shredded). Set aside.
Melt the butter in a small bowl, set aside.
In a small bowl, mash the banana, then whisk in the eggs, shredded carrots, and milk. Set the bowl aside.
In a large mixing bowl, whisk together the oats, flour, baking powder, baking soda, brown sugar, and pumpkin spice.
Add the wet ingredients bowl to the dry ingredients. Mix with a spoon until just combined. Don't over mix. Add the melted butter and mix. The batter should be thick but if it's too thick you can add more milk.
Generously spray a muffin tin with cooking spray. You can use liners, just be sure to spray the liners. Scoop a large spoonful into each. I like to use a large cookie scoop, linked above in the post.
Bake in the oven at 350 degrees for 15 minutes. Serve with butter on top.. Enjoy!