1cupmilk of choicesee note #2 to make it a mocha smoothie
Combine the frozen banana, milk, peanut butter, cocoa powder and ground flaxseed in a blender. Blend until smooth and creamy. Add extra milk as needed to thin.
Banana: I like to use frozen banana because it makes the smoothie creamier and colder. Slice and freeze on a cutting board for 2-3 hours. You can use an unfrozen banana too, just blend in 1-2 cubes of ice as needed to chill the smoothie.
Mocha option: I love to do ½ cup milk and ½ cup coffee to make a mocha smoothie. Make sure the coffee is chilled before adding to the blender.
Sweetener: If your banana isn't very ripe the smoothie may not be sweet enough. You can add liquid sweetener like maple syrup or agave syrup 1-2 teaspoons at a time.