Begin by placing an oven rack in the upper third of the oven. Preheat the oven to 350 degrees F. Grease and flour a 10-inch ovenproof skillet.
Then, in a medium-size bowl, whisk together the flour, baking soda, and salt.
In the bowl of an electric mixer using the paddle attachment, cream together the butter and sugars on medium speed until light and fluffy, about 3 - 4 minutes. Reduce the speed to low; then add the egg, followed by the egg yolk and vanilla. Beat well. Add the flour mixture and beat on low until just combined.
Using a spatula, fold in the chocolate chips until just combined. Add the batter to the prepared pan and smooth out the top. Add a few more of your chips to the top of the batter, if desired.
Bake until the cookie is lightly browned on the outside, but still slightly under-cooked in the center. This will take about 20 - 22 minutes. Allow the cookie to cool for 10 - 15 minutes before serving.
Slice up and serve with a scoop of vanilla ice cream.
Notes
*You can use whatever chips, nuts, etc. that you like. I recommend about 1 1/2 cups total. I also sprinkled a few on top of the cookie before baking so I could easily tell what was inside the cookie.