I made a large 14" diameter round pan, but had made about 10 cookies from the recipe first. It was still almost 2" thick. So, if you use the whole recipe for a 14" circle or 9x13" pan, you will get a thicker cookie that's more like a blondie. If you put the whole recipe into a larger half-sheet (or lasagna) pan, then it will be thinner, but still a thick cookie. Whatever pan you use should have at least 2-3" sides.
You may want to turn a 14" circle or 9x13" pan out onto a cake board to serve (anything larger, you'll probably want to serve from the pan). When the cookie is COLD, put a tray over the pan and flip the cookie onto the tray. Then put your cake board on the cookie, and flip it back onto the cake board you want to serve it from.
GIANT CHOCOLATE CHIP COOKIE
1 box butter cake mix...........................................2 eggs
about 2 TB caramel ice cream topping or syrup
1 stick (8 TB) butter, melted.................................1 12-oz. package chocolate chips
(NOTE: I like to combine mini-morsels with milk chocolate chips ~ Here I combined mini-morsel with Holiday red & green chips)
OPTIONAL: SPRINKLES
about 1/2 cup flour (or may need a little more)
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Preheat oven to 350. Spray whatever pan you're using very well with non-stick baking spray (containing flour). IF your pan is old and never gets quite clean any more AND you're planning to turn the cookie out of the pan to serve on a platter, you also might want to cut a piece of parchment paper to fit the bottom of the pan, and then spray that too.
Put everything else into your blender and gradually beat until the flour is incorporated (if you want to add sprinkles to the batter, about 1/4 cup, but they'll probably sink during baking, so I sprinkle some on top about halfway through baking). Then raise the speed to medium, and beat until the dough somewhat comes together around the paddle and isn't very sticky when you touch it. (If it's sticky, add a few more TB flour and beat that in.)
Dump the dough into your prepared pan and spread evenly to the sides. Bake for at least 10-12 minutes (maybe 5-7 minutes longer if your batter is thicker and you're making blondies, rather than a cookie). Let it cool. I gave directions above for turning it out onto a cake board, if you want.