Slice the banana into coins for easier blending. If you prefer an extra thick smoothie, freeze the slices for at least 1 hour beforehand.
Add the Greek yogurt to the blender first. This helps the blades move smoothly and prevents sticking.
Add the banana slices, peanut butter, milk, honey (if using), vanilla extract, and seeds (if using).
Drop in the ice cubes last.
Blend on high for 30 to 60 seconds, or until completely smooth and creamy with no visible lumps.
Check the consistency. Add a splash more milk if it’s too thick, or a few more ice cubes if you want it thicker. Blend again briefly.
Taste and adjust sweetness if needed.
Pour immediately into a tall glass and serve chilled.