Begin by washing the fresh spinach leaves thoroughly under cold running water to remove any dirt or sand.
Place the washed spinach leaves into the blender.
Add the sliced banana, almond milk, Greek yogurt, honey (if using), vanilla extract, and ice cubes to the blender.
Blend on high speed until the mixture is smooth and creamy, about 1-2 minutes. If the smoothie is too thick, you can add more almond milk to reach your desired consistency.
Once blended, taste the smoothie and adjust sweetness by adding more honey if needed.
Pour the smoothie into glasses and serve immediately.
If desired, add protein powder or nut butter for an extra protein boost before blending.
For a greener smoothie, consider adding a few extra spinach leaves.
Store any leftovers in the refrigerator for up to 24 hours, but it's best enjoyed fresh.