01 - Add the milk, yogurt (if using), frozen banana, peanut butter, cocoa powder, and sweetener to a blender.
02 - Add the ice cubes and any optional add-ins to the blender.
03 - Blend on high speed until the mixture is smooth and creamy, scraping down the sides as needed.
04 - Taste the smoothie and adjust sweetness or thickness by adding more sweetener, ice, or milk as desired.
05 - Pour the smoothie into two glasses and serve immediately.