Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease each cup.
In a blender or food processor, blend the fresh spinach leaves with almond milk until smooth.
In a large mixing bowl, combine the blended spinach mixture, mashed bananas, maple syrup (or agave nectar), melted coconut oil, and vanilla extract. Mix until well combined.
In a separate bowl, whisk together the gluten-free all-purpose flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.
Spoon the batter into the prepared muffin cups, filling each about 3/4 full.
Sprinkle additional chocolate chips on top of each muffin if desired.
Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.