Preheat the air fryer to 325°F (163°C).
In a small mixing bowl, whisk together the protein powder, oat flour, baking powder, sweetener, and sea salt until combined.
Stir in the unsweetened applesauce, liquid egg white, and vanilla extract until a thick, cohesive dough forms.
Fold in the sugar-free chocolate chips.
Line the air fryer basket with a small square of perforated parchment paper.
Shape the dough into a ball and place it on the parchment, pressing down slightly to form a disk approximately 1/2-inch thick.
Air fry at 325°F (163°C) for 6 to 8 minutes, or until the edges are firm and the top is just set.
Let the cookie rest in the air fryer basket for 3 to 5 minutes to firm up before transferring to a cooling rack.