Combine the ground flaxseed and water in a small bowl. Stir thoroughly. Let sit for about 5 minutes, until the mixture thickens. This forms a 'flax egg.'
For the brownie layer: Set a piece of parchment paper in the bottom of your air fryer. Combine the brownie mix, ½ of the flax/water mixture, 1 T vegetable oil and pinch of baking powder. Stir to combine. Roll this mixture into 3 balls, and use your palm to flatten them slightly. Each piece should be about 2 inches in diameter. Set each brownie piece onto the parchment paper.
For the cookie layer: In a separate bowl, combine the cookie mix, the remaining flax/water mixture, 1 T vegetable oil and pinch of baking powder. Stir to combine. Roll this mixture into 3 balls, and use your palm to flatten them slightly. Place each cookie directly on top of each brownie.
Air fry at 320 degrees for ~8 minutes.
