In a large bowl whisk together almond flour, coconut flour, baking soda, salt, and cinnamon.
In a small bowl mash the banana with a fork. Stir in the egg, sugar, coconut oil and vanilla. Make sure you stir well to combine.
Add the wet ingredients all at once to the dry and stir until well combined.
The dough is a stickier dough. Place the dough in the fridge and chill for about 15-20 minutes (this will help to scoop out the dough portions. If you have even more time, you could chill for even an hour).
While the dough is chilling, heat up oven to 350F. Line a baking sheet with parchment paper. Spray with some baking spray or grease it with some oil (or margarine).
When ready to bake, remove the dough from the refrigerator. Use an ice cream scooper or a spoon to scoop out portions of the dough. Use your hands to roll them into balls and place each dough ball on the baking sheet.
Place balls on parchment lined baking sheets. Space them 1 1/2 inches apart. Press down gently with your hands to flatten each portion of dough into 5-cm/2-inch wide/1/2 inch thick cookies. You should have about 12-14 cookies (I rolled out 12, if you roll them smaller, you could get 14).
Bake for 13-16 minutes, until cookies are pale on top and lightly golden on the bottom. Bake another couple minutes if the tops seem too soft and the color still too light on the edges (they shouldn’t be completely brown).
Transfer cookies to a wire rack to cool for 10 minutes.
While the cookies cool, prep the icing. In a small bowl, whisk together the confectioners’ sugar and almond milk until it forms a thick but pourable glaze (add more milk if necessary). If it gets too thin, add a little more confectioners' sugar. Drizzle on each cookie, add the sprinkles and let set, about 15 minutes.