In a high-speed blender, combine spinach or kale, banana, almond milk, cocoa powder, and protein powder if desired. Blend on high for about 30 seconds until well incorporated.

Add a handful of ice cubes to the blender based on thickness preference. Blend again for 20-30 seconds until frosty and creamy.

Taste the smoothie. Adjust sweetness or thickness by adding more almond milk or banana as needed, blending again.

Pour the smoothie into a tall glass. Add toppings like granola or chia seeds if desired. Serve immediately.