Preheat oven: Turn it to 350°F (177°C).
Get pan ready: Grease a 9-inch pie dish or round cake pan with nonstick spray.
Mix butter: Beat it until it's soft and creamy.
Add sugar: Mix it in until it's creamy too.
Put in eggs and vanilla: Mix until they're all combined.
Mix dry stuff: In another bowl, mix flour, cornstarch, baking soda, and salt.
Combine wet and dry: Slowly mix the dry stuff into the wet stuff until it's all mixed up.
Add chocolate chips: Mix them in until they're spread out.
Squish dough: Push the dough evenly into the pan.
Bake it: Stick it in the oven for 20-25 minutes until it's a bit golden.
Check if it's done: Poke it with a toothpick; if it comes out clean, it's ready.
Stop it from burning: If the edges get too brown too quickly, cover them with foil.
Cool it down: Let it cool on a rack.
Serve it up: If you want, move it to a plate.
Add toppings: You can put frosting, whipped cream, or ice cream on top.
Keep it fresh: Cover it up and it can stay good for up to 3 days at room temperature.