Preheat oven to 400° degrees F. Line 2 baking sheets with parchment paper or silicone liners; set aside.

In a medium bowl, whisk together the dry ingredients of cornstarch, baking soda, salt, and all-purpose flour; set aside.

In a large mixing bowl, using a mixer, cream together the butter and both sugars until mixture is light and fluffy. Beat in the eggs and vanilla and beat together until combined.

Add the flour mixture to the wet mixture and mix on low speed until just incorporated. Add in the mini m&m’s and mini chocolate chips and any other add-ins you want to add in and mix until just combined.

Using a ¼ cup cookie scoop, scoop cookie dough onto your parchment lined cookie sheet, then place another ¼ cup of the cookie dough on top, so you have a double scoop (1/2 cup worth of cookie dough). You should get 9-10 cookies. Place cookie sheet with cookie dough mounds in the refrigerator for 15-20 minutes, to get the super thick cookies you're dreaming about! Of course, you don't have to chill the cookie dough, they will still be thick, so it's up to you what your preference is!

Once the dough is chilled, place cookies 3″ apart on a lined baking sheet. Do 4 – 6 per cookie sheet.

When baking cookies, put one sheet in the middle of the oven and bake for 8-12 minutes, checking at 8 minutes. The cookies should look dry on top and almost done with a little bit of gooeyness in the middle. If they need more time, bake them longer.

Let the cookies cool on the baking sheet for at least 30 minutes before eating. They will finish cooking and firm up while they cool, and they can break easily when they are hot.