Heat oven to 325 degrees F.

Add butter to a microwave safe bowl and microwave for about 45 seconds, or until most of it has melted. Allow it to cool for a few minutes.

Add melted butter, granulated sugar and brown sugar to a medium bowl and beat with an electric mixer until well blended.

Add the egg, egg yolk, and vanilla and mix until combined.

Stir in the flour, baking soda, and salt, just until combined. Gently stir in the chocolate chips.

Press the cookie dough into a 10’’ or 12’’ cast iron skillet (or a regular, oven-safe skillet would work).

Bake for 28-35 minutes or until it looks just barely golden. Don’t over-bake it, especially since it will continue to cook in the hot skillet when you take it out of the oven.

Allow to cool in the skillet for at least 20-30 minutes before cutting.

Slice cookie into pieces and serve warm with a scoop of vanilla ice cream, if desired.