In a large bowl, whisk together the flour, baking soda, cornstarch, and salt. Set aside.

In another bowl, whisk the melted butter, brown sugar, and white sugar until smooth. Add the egg, then the egg yolk, and finally, the vanilla. Mix until combined.

Pour the wet ingredients into the dry ingredients. Stir with a spoon or spatula until combined, then fold in the chocolate chips. Cover the dough and chill in the fridge for at least 3 hours, or up to 3 days.

When ready to bake, take the dough out to soften for about 10 minutes. Preheat the oven to 325°F (163°C) and line two baking sheets with parchment or silicone mats.

Roll the dough into 1.5-tablespoon balls. Press a Rolo into the center of each ball, covering completely with dough.

Slightly flatten each ball, add a few extra chocolate chips on top, and sprinkle with sea salt.

Bake each batch for 12-13 minutes until soft. Let cool on the sheet for 10 minutes before transferring to a wire rack.