Preheat the air fryer. Set it to 325°F (163°C) for 3–5 minutes. This helps the cookie cook evenly from the start.
Prep the pan. Lightly grease a 6–7 inch skillet or cake pan. For easy removal, line the bottom with a parchment round.
Mix the wet ingredients. In a medium bowl, whisk the melted butter, granulated sugar, and brown sugar until glossy and combined.
Add the egg yolk and vanilla, and whisk until smooth.
Add the dry ingredients. Sprinkle in the flour, baking soda, and salt. Stir with a spatula until just combined. Don’t overmix; stop when no streaks of flour remain.
Fold in the chocolate. Stir in the chocolate chips or chunks.
For extra pools of chocolate, reserve a few pieces to press on top.
Press into the pan. Spread the dough evenly in the prepared skillet. Press in the reserved chocolate on the surface. If you like, sprinkle a pinch of flaky sea salt.
Air fry. Place the pan in the air fryer basket.
Cook at 325°F (163°C) for 10–13 minutes, until the edges are golden and set, and the center looks slightly soft and puffed. For a gooier cookie, start checking at 9–10 minutes.
Rest briefly. Remove the skillet and let it sit for 5–7 minutes. The carryover heat finishes the center without overbaking.
Serve warm. Top with ice cream or your favorite sauce and serve straight from the skillet with spoons.