Line a 6-inch square or round cake pan with parchment paper, leaving enough overhang to easily lift the brownies out after baking.
In a microwave-safe bowl, combine the butter, granulated sugar, brown sugar, and cocoa powder.
Microwave in 20-second intervals, stirring after each interval, until the butter is melted and the mixture is smooth.
Let the mixture cool for 2-3 minutes, then stir in the vanilla extract.
Add the egg and whisk until fully incorporated.
Stir in the flour just until combined. Do not over mix.
Fold in half of the chocolate chips.
Pour the batter into the prepared pan and spread it into an even layer. Sprinkle the remaining chocolate chips over the top.
Air fry for 15 minutes. Check for doneness by inserting a toothpick into the center (avoiding the melted chocolate chips). If needed, continue cooking in 2-3 minute intervals until the edges are set and the center is cooked through.
Let the brownies cool in the pan for 10-15 minutes.
Lift the brownies out using the parchment paper, slice into 12 pieces, and serve.
Notes
Each air fryer cooks differently so the bake times will vary. Make sure to check regularly until the brownies are cooked through. Leftover brownies can be stored in an airtight container or bag at room temperature for up to 5 days.