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.
Video
Notes
Make ahead Instructions: The cookie dough can be made ahead and stored in the refrigerator for 1-2 days or frozen for 2-3 months.Freezing Instructions: Allow the skillet cookie to cool completely and slice into wedges. Store wedges in air-tight freezer container for 2-3 months. Other Variations:
Mini skillet cookie: Use a smaller, oven-safe pan or ramekins to make mini skillet cookies. Reduce the bake time.
Vary the chips: Substitute white chocolate or butterscotch chocolate chips. I like to add a little milk chocolate AND semi-sweet chocolate chips to my cookie dough. Sometimes I'll add them in different sizes too, like mini chocolate chips or chocolate chunks.