Prep your pan and air fryer: Lightly grease two ramekins or one small pan with nonstick spray or butter. Preheat your air fryer to 320°F (160°C) for 3–5 minutes.
Whisk the wet ingredients: In a bowl, whisk melted butter, granulated sugar, and brown sugar until glossy, about 30 seconds.
Add the egg and vanilla, and whisk until slightly thick and smooth.
Add the dry ingredients: Sift or sprinkle in cocoa powder, flour, and salt. Gently fold with a spatula until just combined. The batter will be thick and shiny.
Stir in chocolate: Fold in mini chocolate chips.
Don’t overmix.
Fill the pan: Divide the batter between the two ramekins or spread in one small pan, smoothing the top. For extra gooey centers, press a few extra chips on top.
Air fry: Place the pan(s) in the air fryer basket. Cook at 320°F (160°C) for 10–13 minutes for ramekins or 12–15 minutes for one pan.
Start checking at the earlier time.
Check doneness: The edges should look set and slightly pull away. The center should look glossy and a little soft. A toothpick will come out with a few moist crumbs, not wet batter.
Rest before serving: Let the brownies sit for 5–10 minutes.
This sets the crumb and makes them extra fudgy.
Serve: Enjoy warm as is, or add a scoop of vanilla ice cream and a pinch of flaky salt.