In a large bowl, whisk the flour, baking soda, cornstarch, and salt together until well combined.

In another medium bowl, whisk the melted butter, brown sugar, and granulated sugar until smooth without lumps. Add the egg, then the egg yolk, and finally the pure vanilla extract, whisking until everything blends beautifully.

Pour the wet ingredients into the dry mixture. Stir with a large spoon or silicone spatula until the dough comes together, and fold in those chocolate chips.

Cover the dough with plastic wrap and refrigerate for at least 3 hours, or up to 3-4 days.

Once chilled, take the dough out and let it sit at room temperature for about 10 minutes. Preheat your oven to 325°F (163°C) and line two large baking sheets with parchment paper.

Roll the dough into balls, using about 1.5 tablespoons of dough each (aim for 30 cookies). Create a thumbprint in the center of each ball, insert a Rolo candy, then cover it with another piece of dough.

Gently flatten each cookie dough ball and press a few extra chocolate chips on top. Finish with a sprinkle of coarse sea salt or flaky sea salt.

Place 7-8 of the dough balls on each cookie sheet, refrigerating one sheet while you bake the first batch. Bake for 12-13 minutes.

Allow the cookies to cool on the cookie sheet for about 10 minutes. Then, transfer them to a wire rack to cool completely.