Preheat your oven to 350°F (175°C). Melt ½ cup unsalted butter in a cast-iron skillet over medium heat until golden brown, about 5-7 minutes.

In a mixing bowl, combine browned butter with ¾ cup brown sugar and ¼ cup granulated sugar, whisking until smooth. Stir in 1 tablespoon vanilla extract, 1 egg, and 1 egg yolk.

In another bowl, whisk together 1.5 cups all-purpose flour, 0.5 teaspoon baking soda, and 0.5 teaspoon salt. Gradually combine with wet ingredients.

Gently fold in 1 cup chocolate chunks or chips, reserving some for the top.

Press the cookie dough into the skillet, sprinkle reserved chocolate on top, and ensure an even shape.

Bake in the preheated oven for 20-25 minutes until edges are golden and center is slightly soft.

Allow to cool for 5-10 minutes before serving directly from the skillet.