Cream the butter and sugars: In a mixing bowl, beat the softened butter, granulated sugar, and brown sugar until smooth and slightly fluffy, about 1–2 minutes by hand or with a hand mixer.

Add egg and vanilla: Mix in the egg and vanilla until fully combined. Scrape down the sides of the bowl.

Whisk the dry ingredients: In a separate bowl, whisk the flour, cocoa powder, baking soda, and salt to break up any lumps.

Combine wet and dry: Add the dry ingredients to the wet and stir just until no dry streaks remain. If the dough seems stiff or crumbly, add up to 1 tablespoon milk to bring it together. Fold in the chocolate chips or chunks.

Preheat the air fryer: Set to 320°F (160°C). Preheating helps the cookies set with crisp edges.

Prepare the basket: Line the air fryer basket with a parchment liner or lightly mist with nonstick spray. Leave room around the edges for air circulation.

Portion the dough: Scoop 1.5 to 2 tablespoons of dough per cookie (about a medium cookie scoop). Roll into balls and flatten slightly to about 1/2 inch thick. Space them at least 1.5 inches apart. You’ll likely need to bake in batches.

Bake: Air fry at 320°F for 6–8 minutes. Cookies should look set at the edges and slightly soft in the center. They’ll firm up as they cool. If your air fryer runs hot, start checking at 5 minutes.

Finish and cool: If using, sprinkle a pinch of flaky sea salt over the hot cookies. Let them cool in the basket for 3–4 minutes before transferring to a rack to finish cooling. Repeat with remaining dough.

Serve: Enjoy warm while the chocolate is gooey, or let cool completely for chewier centers.