Preheat the oven to 350 degrees Fahrenheit (177 degrees Celsius). Line the cookie sheets with parchment paper and set aside.

In the bowl of a stand mixer, combine the sugars and butter. Beat until fluffy (about 2 minutes). Add the vanilla and one egg, mixing until just combined. Add the second egg and mix until incorporated.

In a medium-sized mixing bowl, whisk together the flour, baking soda, baking powder, cornstarch, and salt. With the mixer on low speed, gradually add the dry ingredients, mixing until no flour pockets remain.

Remove the bowl from the stand and fold in the chocolate chunks. Be sure to include all the shards or shavings from chopping the bars – that’s what makes these “freckled!” Place the dough into the refrigerator to chill for 1 hour. Remove and let stand for 5 minutes before scooping and placing onto the prepared sheets.

Place in the oven and bake for 10–12 minutes – the edges will become light brown, and the centers should still look slightly soft and gooey. They’ll firm up once they’ve cooled a bit. Remove from the oven and let cool on the sheets for 3 minutes, then transfer to a wire rack to cool completely.