Air Fryer Chocolate Frosted Fudge Brownies

Line a 7-inch pan with parchment and preheat the air fryer to 320°F.
Melt 0.5 cups unsalted butter and 1 cups semisweet chocolate chips together in the microwave in 30-second bursts. Let the mixture cool for 2 minutes so it doesn't scramble the eggs.
Whisk in 0.8 cups granulated sugar, and 0.3 cups light brown sugar vigorously until the mixture is glossy.
Add 2 large eggs one at a time, then 1.5 teaspoons vanilla extract. Whisk until smooth.
Sift in 0.5 cups all-purpose flour, 0.3 cups unsweetened cocoa powder, and 0.5 teaspoons fine salt. Fold gently with a spatula until no streaks remain. Stop the second the flour disappears — overmixing makes tough brownies. Slowly fold in 0.3 cups mini chocolate chips.
Pour into the pan, smooth the top, and air fry for 22-26 minutes. Check at 22.
Cool completely on a wire rack — at least 45 minutes. Frosting warm brownies turns the frosting into a glaze.
Make the frosting while the brownies cool. Beat softened 0.3 cups unsalted butter until smooth, then add 0.3 cups unsweetened cocoa powder, 1.5 cups powdered sugar 2 tablespoons whole milk or heavy cream, 0.5 teaspoons vanilla extract, and 1 pinch fine salt. Beat 2-3 minutes until fluffy.
Spread frosting thickly over the cooled brownies, swirl with the back of a spoon, let set 15 minutes, and slice into 9 squares.