Preheat the oven to 350 degrees and grease a mini muffin pan with cooking spray.
Add the banana, milk, peanut butter, egg, applesauce, spinach and vanilla extract to a food processor or blender. Pulse until the spinach is chopped into very fine pieces. Stop to scrape down the sides as needed.
Add the flour, baking soda, cinnamon and salt to the food processor. Blend until fully combined stopping to scrape down the sides as needed.
Add about 2 tbsp of batter to each mini muffin cup. Place in oven and cook for 15 minutes.
Let cool and enjoy! Store in an airtight container in the refrigerator.
Recipe by Kiss by Brooke at https://www.kissbybrooke.com/2020/02/06/spinach-banana-mini-muffins/