Gather all ingredients and make sure your banana is peeled and frozen if using. Chop the dark chocolate into small pieces for garnishing later.
Add protein powder, flaxseed, banana, spinach, peppermint extract, almond milk, coconut nectar, and ice cubes into the blender. Blend on high until smooth and creamy.
If the smoothie is too thick, add more almond milk, one tablespoon at a time, until desired consistency is reached.
Pour the smoothie into a glass. Sprinkle chopped dark chocolate on top and optionally create a chocolate swirl using melted chocolate for a fancy touch.