Preheat the air fryer to 310ºF for 5 minutes.

In a medium bowl, combine the peanut butter, butter, and sweetener. Beat until well combined and smooth. Add the egg and vanilla and beat for 30 seconds until well combined.

Add the almond flour, collagen powder, baking soda, and salt, and beat until well combined into a dough.

If using chocolate chips, stir them in evenly.

Divide the dough into two even portions, then roll each portion into 4 balls. Place 4 of the balls onto a piece of parchment (or a parchment air fryer liner) and press down to about 1/2 inch thick. Use a fork to create a cross hatch pattern on the cookies, if desired.

Set the air fryer to Bake and set the parchment paper on the air fryer crisper rack. Cook at 310ºF for 8 to 10 minutes, until puffed and golden brown. Remove and let cool completely for 15 minutes.

Repeat with the remaining cookie dough, or wrap it tightly in plastic and refrigerate for up to 5 days.