Preheat your air fryer to 370 degrees F for 5 minutes.
In a medium bowl, whisk together 4 tablespoons of melted and cooled salted butter and ⅓ cup of brown sugar until well combined.
Add 1 large egg yolk and 1 teaspoon of vanilla extract. Whisk to combine.
Add ¾ cup of all-purpose flour and ½ teaspoon of baking soda. Mix just until no large lumps of flour remain.
Fold in ½ cup of semisweet chocolate chunks until fully incorporated.
Line the air fryer basket with parchment paper and use a 1.5 tablespoon scoop to portion out 6 cookie dough balls.
Cook for 6-8 minutes, or until the cookies are golden brown and crisp.
Remove the cookies to a wire rack to cool and repeat steps with remaining dough.
Enjoy warm or at room temperature. Store in an airtight container at room temperature for up to three days.
