- Preheat oven to 350 F, and line a muffin pan with paper liners (or use silicone muffin cups sprayed with cooking spray).
- Combine all dry ingredients in a large mixing bowl.
- Heat the butter until just melted. Using a blender or food processor, blend the raw spinach, banana, honey, milk, egg, vanilla, and melted butter until completely pureed.
- Pour the puree into the dry ingredient bowl, and fold together gently until just combined. (Do not over-mix.)
- Spoon the batter into the muffin pan, and bake for 18-22 minutes, or until the muffins are firm to the touch on top, but not quite browning.
- Cool most or all of the way before serving.