Using a stand or a hand mixer, cream together the butter & sugars for 2-3 minutes.
If you're using a stand mixer and your hands are free, you can whisk together the dry ingredients (flour, baking soda, salt) in a separate mixing bowl and set aside.
Add the vanilla & egg to the creamed butter/sugar & mix briefly - just until the egg is blended in. Scrape the sides of the bowl to make sure everything is evenly mixed.
Gently add in the flour mixture and mix just until blended.
Fold in the chocolate chunks & chips.
Cover the dough with plastic wrap, and set bowl in the fridge to chill for 30-60 minutes.
Remove dough from fridge & preheat oven to 350.
Lightly butter a 12" cast iron skillet (see notes in post about using a pizza pan if you don't have a cast iron) and press dough evenly across the pan.
Sprinkle Christmas sprinkles across the top.
Bake dough in skillet for 20 minutes at 350.
Remove from oven, and set aside to cool and set before serving.