Preheat the oven to 325ºF/163ºC.
Brown the butter: add the butter into a large frying pan and cook over medium heat until the butter melts, stirring occasionally. Once it begins to simmer, continue cooking for another 2-3 minutes while stirring constantly. The melted butter will start to foam on top, then will turn light brown in color and smell deliciously nutty. Remove from heat at this point and transfer to a glass container to cool slightly (about 5-10 minutes).
Add the C&H® Dark Brown Sugar and Granulated Sugar into a large mixing bowl, then pour the brown butter on top. Whisk until well blended. Add the egg, egg yolk, and vanilla and whisk until smooth and combined.
Add the flour, baking soda, and salt. Fold into the wet ingredients until a uniform dough forms, then fold in the chocolate chips.
Press the cookie dough into a 10’’ cast iron skillet (or another regular, oven-safe skillet) and bake for 28-32 minutes, until it looks barely golden. It’s important not to over-bake it, since it will continue to cook in the hot skillet after you take it out of the oven.
Allow to cool in the skillet for at least 20-30 minutes before cutting. Slice into pieces and serve warm with a scoop of vanilla ice cream, if desired.