In a blender or food processor, blend fresh spinach leaves and ripe bananas until you have a smooth, green puree.
In a mixing bowl, whisk together the flour, baking powder, cinnamon (if using), and salt.
In a separate bowl, combine the spinach-banana puree with milk, egg, maple syrup or honey, and vanilla extract. Mix well.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix.
Heat a griddle or non-stick skillet over medium heat. Add a small amount of butter or olive oil to coat the surface.
Pour 1/4 cup of batter onto the griddle for each pancake. Cook until bubbles form on the surface, then flip and cook the other side until golden brown.