Preheat oven to 350°F (175°C). Lightly grease a 10-inch oven-safe skillet.
In the skillet, whisk together melted butter, brown sugar, and granulated sugar until smooth.
Add the egg and vanilla, stirring until fully combined.
Sprinkle in flour, baking soda, and salt. Stir just until no dry streaks remain.
Fold in chocolate chips, reserving a small handful for the top.
Spread the dough evenly in the skillet and sprinkle remaining chips over the surface.
Bake for 18–22 minutes, until edges are set and the center is slightly soft.
Remove from oven and let cool for 10 minutes before serving.