Melt half of the butter in a saucepan over low heat. In a mixing bowl, combine melted butter with softened butter, brown sugar, and granulated sugar; cream until light and fluffy—about 2-3 minutes.

Add eggs one at a time, mixing well after each addition, followed by the vanilla extract. In a separate bowl, whisk together flour, cornstarch, baking soda, and salt, then mix gradually into wet ingredients.

Fold in chocolate chips and refrigerate the dough for at least 30 minutes.

Prepare the brownies by cutting them into small chunks or squares.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Take a portion of the chilled cookie dough, flatten it in your palm, place one brownie chunk in the center, encase it with more dough, and roll it back into a ball.

Arrange the cookie dough balls on the baking sheet, leaving space between each for spreading.

Bake for 11 minutes, rotating halfway through. The cookies should look slightly under-baked at the edges.

Let them cool on the baking sheet for about 5 minutes before transferring to a wire rack.