Preheat your oven to 350 degrees F. Place nine 4-inch shallow paper baking cups onto a large baking sheet and spray the insides with non-stick cooking spray. Set aside.
Add the butter and both sugars to a large mixing bowl. Beat together for 3 minutes until fluffy. (You can also do this in your stand mixer fitted with the paddle attachment.)
Add the eggs and vanilla and mix until combined.
Whisk the flour, cornstarch, baking powder, and salt in a medium mixing bowl. Slowly add the flour mixture to the wet ingredients while mixing at low speed until the flour is incorporated.
Add the mini chocolate chips and 1/2 cup of chocolate chunks to the cookie dough and fold in with a rubber spatula until the chocolate is evenly distributed. Do not overmix.
Place 1/2 cup of cookie dough into each baking cup. Then, gently press the dough into the bottom of each cup so it's spread into an even layer.
Divide the remaining 1/2 cup of chocolate chunks evenly among the cookies and press them into the top of the cookies.
Bake for 20 to 25 minutes (see note) or until golden brown. Remove from the oven and cool for 5 minutes on the baking sheet before transferring to a wire rack to cool completely.
Notes
The original Disney recipe calls for a cooking time of 20-22 minutes. I find that these cookies take 22-25 minutes in my oven. So start checking them at 20 minutes.