In a high-speed blender, combine frozen banana slices, peanut butter, chocolate protein powder, ground flaxseed, and the lower amount of non-dairy milk.
1 ½ cups (200 g) banana, 3 tablespoons (45 g) peanut butter, 6 tablespoons (40 g) vegan chocolate protein powder, ½ - ¾ cup (120 - 180 ml) non-dairy milk, 2 tablespoons (14 g) ground flaxseed