Prep your pan and air fryer: Lightly grease a 6- to 7-inch round cake pan, 6-inch square pan, or a small metal pan that fits your air fryer basket. Line the bottom with parchment for easier removal. Preheat the air fryer to 325°F (163°C) for 3–5 minutes.

Melt the butter: In a microwave-safe bowl, melt the butter until just liquid, not sizzling. Let it cool 1–2 minutes so it’s warm, not hot. Warm butter helps dissolve the sugars and builds that crinkly top.

Whisk in sugars: Add granulated sugar and brown sugar to the warm butter. Whisk for 30–45 seconds until glossy and slightly thickened. This step helps create shiny, crackly tops.

Add eggs and vanilla: Whisk in the eggs and vanilla until smooth and slightly lighter in color, about 30 seconds. Don’t overbeat.

Mix dry ingredients: In a small bowl, whisk together flour, cocoa powder, salt, and baking powder to break up any lumps.

Combine wet and dry: Fold the dry mixture into the wet ingredients with a spatula until just combined. Stop when no dry streaks remain. Stir in chocolate chips if using.

Pan and smooth: Spread the thick batter into the prepared pan. Smooth the top with a spatula so it cooks evenly.

Air fry: Place the pan in the air fryer basket. Cook at 325°F (163°C) for 18–22 minutes, depending on pan size and your air fryer model. Start checking at 16 minutes.

Check doneness: Insert a toothpick near the center. You want moist, fudgy crumbs—not wet batter. The edges should be set and slightly pulling away from the sides.

Cool for best texture: Let the brownies cool in the pan for 15–20 minutes. For the cleanest slices and maximum fudginess, cool to room temperature or chill for 30 minutes before cutting.