Remove the bananas from the freezer and let them thaw 5 minutes to soften them. Roughly chop them into 2-3 inch pieces. Place the bananas and matcha green tea (and agave, if using) in a blender and process until smooth and creamy. You might need to scrape down the sides with a spoon to get everything to blend. Serve immediately.
Use 2 large bananas or 3 small bananas. The nutrition facts are estimated for 2 medium-large bananas, without adding additional sweetener.