Line a 6" circular cake pan with parchment paper.

In a medium mixing bowl, stir together the flour, cocoa powder, and salt. Set aside.

In a large mixing bowl, stir together the melted oil, sugar, and vanilla extract. Once combined, add the egg and stir just until combined.

Add the dry mixture to the wet and stir just until almost no streaks of flour remain. Do not overmix! Fold in 1/4 cup chocolate chips.

Preheat the air fryer to 340 °F (170 °C).

Pour the batter into the prepared pan and sprinkle mini chocolate chips on top. Bake for 12-15 minutes or until the brownies have formed a thin crust and appear set in the middle. A toothpick inserted into the center will come out wet. A toothpick inserted into the sides will come out with some moist crumbs on it, but not totally raw batter. The brownies will continue to bake as they sit in the pan and will firm up as they cool.

Let cool completely and then cover and store at room temperature for up to 4 days. You can also refrigerate them to give them a fudgier texture.