Cream the butter and sugars. In a medium bowl, beat softened butter, granulated sugar, and brown sugar until smooth and slightly fluffy, about 1–2 minutes. This helps dissolve the sugars and builds structure.

Add egg and vanilla. Mix in the egg and vanilla until fully combined and glossy. Scrape down the bowl so everything blends evenly.

Whisk dry ingredients. In a separate bowl, whisk flour, cocoa powder, baking soda, salt, and cornstarch. Breaking up cocoa lumps now makes a smoother dough later.

Combine wet and dry. Add the dry mixture to the wet ingredients and mix on low until no dry streaks remain. The dough will be thick—this is good for fudgy centers.

Fold in chocolate. Stir in chocolate chips or chunks. Reserve a few to press on top for a bakery-style look.

Chill briefly (optional but helpful). Chill the dough for 20–30 minutes. This makes the dough easier to handle and keeps cookies from spreading too much in the air fryer.

Prep the air fryer. Preheat to 320°F (160°C) for 2–3 minutes. Line the basket with air-fryer-safe parchment or lightly mist with oil. Avoid heavy grease—cookies don’t need it.

Portion the dough. Scoop 1.5–2 tablespoon mounds (about a medium cookie scoop). Roll gently into balls and flatten slightly to 1/2–3/4 inch thick. Space them well—work in batches of 4–6, depending on your basket size.

Air fry. Cook at 320°F (160°C) for 6–8 minutes. They’re done when edges look set but centers still appear soft. Add 30–60 seconds if needed, but don’t overbake.

Finish and cool. Immediately press a few extra chips on top and sprinkle with a pinch of flaky salt, if using. Let cookies rest in the basket for 3–4 minutes to firm up before moving to a rack.

Repeat. Continue with remaining dough. Enjoy warm or at room temp.