Make the flax egg: Stir together the flaxseed meal and water. Let sit for 5 minutes, then stir again.
In a large bowl, mix together the banana, maple syrup, chocolate peanut butter, and milk. Add the remaining ingredients and mix until well combined.
Transfer to the refrigerator and chill for about 30 minutes.
Use a cookie scoop to dollop the dough 1-2 inches apart on a large baking sheet. Bake for 10-12 minutes or until firm to the touch and a toothpick inserted into the center comes out clean. Let cool and enjoy!