Preheat your oven to 325 degrees F. This temperature is key for ensuring your cookie bakes evenly and achieves that perfect golden color.
Add butter to a microwave-safe bowl and heat it for about 45 seconds. You want most of it melted—this will help your cookie achieve the right texture. Once melted, allow it to cool slightly for a few minutes.
In a medium bowl, combine the melted butter with granulated sugar and brown sugar. Use an electric mixer to beat the mixture until well blended. You’re aiming for a smooth, creamy consistency.
Add the egg, egg yolk, and vanilla to the bowl. Mix until everything is combined. This step is crucial as it brings all the liquids together, ensuring a moist cookie.
Now, it’s time to add the dry ingredients. Gradually stir in the flour, baking soda, and salt until just combined. Be careful not to over-mix, as this can make the cookie tough.
Gently fold in the chocolate chips. You want to ensure they are evenly distributed throughout the dough.
Press the cookie dough into a 10-inch or 12-inch cast iron skillet. If you don’t have a cast iron skillet, an oven-safe skillet will work fine too. Make sure to spread it evenly, as this will help it bake uniformly.
Place the skillet in the preheated oven and bake for 28 to 35 minutes. Look for a barely golden top; it’s okay if it looks a little underbaked, as it will continue to cook while cooling.
Once done, remove the skillet from the oven and let the cookie cool for at least 20 to 30 minutes before cutting. This waiting period ensures that it firms up and is easier to slice.
Slice the cookie into pieces and serve warm. For extra indulgence, add a scoop of vanilla ice cream on top—this is a must!