In a medium bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt.
In a large bowl, add the cold butter and beat for about 2 minutes to cream it. Add the brown sugar and granulated sugar, beat on medium speed for 2-3 minutes until combined but not overly fluffy.
Add eggs one at a time, then vanilla extract and vanilla bean paste. Mix just until incorporated.
Add the dry ingredients and mix on low until a thick dough forms.
Fold in the chocolate chunks and chocolate chips
Divide dough into 10–12 large portions (about 5–6 ounces). Shape each portion into a rough, tall mound rather than a smooth ball. This helps create the thick bakery-style appearance.
Place on a tray, cover, and refrigerate for at least 12 hours and up to 48 hours.
Preheat oven to 400F. Line two to three baking sheets with parchment paper.
Place only 4–5 cookies per sheet, leaving plenty of room between them. If you have really large baking sheets, this will work with 6 cookies per sheet.
Bake for 12–15 minutes until the edges are golden brown but the centers still look slightly underdone. For smaller cookies (12 cookies), I like to bake them closer to the 12-13 minute mark. For larger cookies (10 cookies), I like to bake them closer to the 14-15 minute mark.
Immediately after baking, use a large round cutter or bowl to gently swirl around each cookie to create perfectly round edges. This technique is called cookie scooting. Allow cookies to cool on the baking sheet for 15 minutes before moving. The centers will continue to set while remaining soft and gooey.