Prep your pan and air fryer. Use a 6- to 7-inch round cake pan or an 8x4-inch loaf pan that fits your air fryer basket. Lightly grease it and line with parchment, leaving overhang to lift the brownies out. Preheat the air fryer to 320°F (160°C) for 3–5 minutes.

Melt the butter. In a microwave-safe bowl, melt the butter until just liquid, not sizzling. You can also melt it on the stovetop over low heat. Let it cool for 2–3 minutes so it doesn’t scramble the eggs.

Whisk in the sugars. Add granulated sugar and brown sugar to the butter and whisk until glossy and slightly thick. This helps create that shiny top.

Add eggs and vanilla. Whisk in the eggs one at a time, then add vanilla. Beat for 30–45 seconds until the mixture looks smooth and a bit lighter. A little air helps with the crackly top.

Combine dry ingredients. In a separate bowl, whisk flour, cocoa powder, salt, and espresso powder (if using) to break up lumps.

Fold together. Add the dry mixture to the wet. Use a spatula to fold until just combined. The batter will be thick. Avoid overmixing—stop when no streaks of flour remain.

Stir in chocolate. Fold in chocolate chips or chunks. Save a few for the top if you like melty pools of chocolate.

Fill the pan. Spread the batter evenly in your prepared pan. Smooth the top and sprinkle on any reserved chocolate.

Air fry. Place the pan in the air fryer basket. Cook at 320°F (160°C) for 16–22 minutes. Start checking at 15 minutes. A toothpick inserted 1 inch from the edge should come out with a few moist crumbs. The center should look set but slightly glossy.

Cool before cutting. Let the brownies cool in the pan for at least 20–30 minutes. For cleaner slices, cool fully, then lift out with the parchment and cut with a sharp knife, wiping the blade between cuts.