Stir together the egg, sugar, peanut butter, and vanilla extract in a medium bowl.

Preheat the air fryer to 350°F, then line the air fryer basket with parchment paper.

Use a tablespoon or small cookie scoop to scoop out the cookie dough. Arrange the dough balls in the air fryer basket, leaving around one inch between each cookie.

Using a fork, mash the cookies down to flatten them.

Cook at 350°F for 6 to 8 minutes, until the cookies are golden brown on the edges.

Allow the cookies to cool in the basket for a few minutes, then transfer to a wire cooling rack to cool completely. Continue cooking in batches until all the dough has been used.