Use a powerful blender for this recipe, one that makes great smoothies and won't leave any spinach leaves unblended!
Blend milk, spinach, yogurt and eggs until smooth. Add the remaining ingredients and blend until fully incorporated (scrape sides if you need to).
Preheat your waffle iron. Spray the waffle iron with nonstick spray.
Pour the waffle batter into your hot waffle iron, being careful not to add too much. Close the lid and cook for 3 to 4 minutes, or until the waffle is cooked through and slightly crispy on the edges. Serve with warm maple syrup.