Preheat your oven to 350°F (175°C). Lightly grease a 6-inch oven-safe skillet with butter or nonstick spray. If you don’t have a small skillet, a mini cake pan or an oven-safe ramekin works too.

In a medium bowl, whisk together melted butter, brown sugar, and granulated sugar until smooth. This step dissolves the sugar into the butter, creating that rich, caramelized flavor.

Next, stir in the egg yolk and vanilla extract. The yolk adds richness, while the vanilla gives the cookie that classic bakery-style taste. Mix until fully incorporated.

Gently fold in the flour, baking powder, cornstarch, and salt. Mix just until the dough comes together—overmixing can lead to a tough cookie!

Stir in the chocolate chips, reserving a few for pressing on top. This ensures those melty pockets of chocolate are visible and evenly distributed.

Spread the dough evenly into the greased 6-inch skillet. Press the reserved chocolate chips on top for that bakery-style look.

Bake for 14-18 minutes, or until the edges are set and golden but the center still looks slightly underdone—this is key for that gooey middle! The cookie will continue to cook as it cools in the skillet.

Sprinkle with flaky sea salt, grab a scoop of ice cream, and dive in straight from the skillet (because why dirty extra plates?).