Preheat oven to 350 F
Add spinach and oats to the blender and blend as much as you can until it's almost a powder.
Add in the banana and egg and blend until just combined. Do not over blend or the mixture will be too airy and won't turn out.
Fold in the chocolate chips.
Spray mini muffin tin with cooking spray. Spoon mixture into muffin tins.
Cook in oven for about 15 minutes.