Preheat the oven to 200C/390F and prepare the muffin trays by lining with wrappers.
Add the eggs and coconut oil to the blender or food processor. Then add in the bananas, broken in to pieces. If using a blender: blend these ingredients first, followed by all remaining ingredients except the mix-ins/toppings. If using a food processor: all of the ingredients except the mix-ins/toppings can be added in one step and blended thoroughly. If there are some lumps in the batter, use a tamper with the blender running or run the food processor again.
Add the mix-ins to the batter and stir with a spatula - this can be done in the blender or food processor after removing the blade.
Pour the batter in to the prepared muffin tin/s. Garnish with any desired toppings. Spray the top of the muffins with coconut oil to prevent burning.
Bake on the middle rack for 15 minutes, reduce the oven temperature to 180C/350F and turn the tray/s around and/or rotate.
Bake for a final 10-15 minutes or until a skewer comes out clean. Ovens can vary quite a lot in temperature, so start with the shortest duration and check on them to ensure they aren't burning. They are done when a skewer comes out clean.
Immediately remove muffins from the tray and cool on a rack.
Can be stored in the refrigerator for up to 5 days.