A powerful mixer or chopper is required. Freeze the cut bananas overnight. The peel should have nice brown spots.
Put the frozen banana pieces and the whole ripe avocado in the blender. Mix until you get a creamy mixture. Possibly add a little water or vegetable milk if the mixture is too thick for the mixer.
Mix the liquid sweetness and matcha powder in a bowl to form a paste. Put the matcha paste in the mixer and mix again on the highest level. Serve immediately and garnish with the desired ingredients, such as fruit or nuts.