Grease a cast iron skillet with butter or nonstick cooking spray.
Use a mixer to beat the butter and sugar together for 1-2 minutes.
Add the whole egg, egg yolk and vanilla and mix thoroughly.
Combine the dry ingredients in a separate bowl.
Combine the wet and dry ingredients to make a dough, being careful not to overmix (it's ok if there are streaks of flour).
Add the chocolate chips and caramel pieces and gently fold into the dough.
Lightly press the dough into a 10 inch cast iron skillet and sprinkle with the coarse sea salt.
Bake for 20-25 minutes, until the edges start to brown and crisp. Remove from oven and let cool for at least 30 minutes.
Notes
Be sure to grease the skillet thoroughly to prevent the cookie from sticking;
If you are using a larger skillet (more than 10"), you will need to bake the cookie for about 15-20 minutes. Once the edges and top are golden brown, that means the cookie should be done;
Don't overmix the dough or the cookie pie will have a tougher consistency - it's ok if you leave a few streaks of flour in the dough;
Be gentle when folding in the chocolate chip and caramel pieces;
You can omit the sea salt sprinkled on the top if desired. I recommend it as I believe it gives the cookie an amazing flavor;
Let it cool before slicing it to make it easier - otherwise it will be very soft and gooey (not always a bad thing though ;-);
See above for some additional mix-in options.
Works in a regular 9x9 baking dish or oven-proof skillet as well if you don't have a cast iron skillet.