In a medium-sized bowl, whisk together the flour, baking soda, cornstarch, and salt. Set aside.
In a large bowl, beat together the cooled melted butter and the sugars with a hand-mixer for about one minute. Then, add in the eggs and vanilla extract. Beat until just combined.
Slowly add in the dry ingredients and mix briefly, just until there are no flour clumps left. Fold in the chocolate chips.
Cover and refrigerate the dough for 30 minutes to an hour.
Brownie Stuffed Chocolate Chip Cookies
If oven is turned off, pre-heat oven to 350 degrees.
Cut the brownies into small 1" x 1" bite sized pieces. Using a cookie scoop, make balls of cookie dough, place on a baking sheet and flatten slightly by making an indent for the brownie.
Place one brownie bite on each indented dough ball. Take an additional tablespoon of cookie dough, flatten to a disk, drape it over the brownie and reform dough into a perfect ball.
Bake on a cookie sheet for 9-11 minutes, or until just barely done and edges are beginning to brown slightly. Cool on a cooling rack and sprinkle lightly with sea salt