Peel and chop the sweet potato. Simmer it in a small pot of water on the stovetop until soft. It will take about 20 minutes.
Drain the sweet potato and mash it. (I used a hand potato masher, but you could use a food processor as well.) You will need 2 tablespoons of mashed sweet potato for this recipe. Refrigerate the rest to use in other recipes.
Place the prepared sweet potato, mashed banana, peanut flour, peanut butter, cocoa powder, baking powder, and ground flax in a food processor. Blend it into a smooth batter. You may need to stop and scrape down the sides of the processor with a spatula several times if the ingredients are sticking to the sides.
Put muffin paper liners in 4 compartments of a muffin tray. Spray the papers with cooking oil. Divide the batter evenly between the prepared muffin papers. Top each with a sprinkle of chopped peanuts.
To air fry: If you have an air fryer oven, place the muffin tray on a rack in the middle of the air fryer. Air fry for 10-12 minutes at 325°F (163°C). After air frying, let the muffins cool in the muffin tin for 30 minutes on the counter to firm up. Then move them to a baking rack for 30 minutes before moving to the fridge.
To oven bake: Preheat the oven to 350°F (177°C). Bake for 20-25 minutes on a rack ⅓ down from the top of the oven. When finished baking, a toothpick inserted into a muffin should come out clean (or with small crumbs).
Important! To optimize your eating experience, let the muffins cool and chill completely before digging in. Enjoy!