01 -
In a stand mixer with paddle attachment, cream softened butter with brown and granulated sugar until light and fluffy, about 3 minutes.
02 -
Add egg and vanilla extract, mix on low until incorporated, then increase to medium-high and beat for 1 minute to emulsify properly.
03 -
Add cornstarch, baking soda, and salt, mixing for 30 seconds. Then add flour 1 cup at a time, mixing until just incorporated after each addition.
04 -
Fold in chocolate chunks either with mixer on low or by hand with a spatula until evenly distributed.
05 -
Preheat oven to 350°F. Line a baking sheet with parchment. Cut croissants horizontally with a serrated knife, leaving the back connected so they open like a book.
06 -
For each croissant, press about 1/2 cup of cookie dough inside the cut croissant, then gently close it. Add remaining dough to the tops of each end.
07 -
Bake for 10-12 minutes until the cookie dough is slightly golden but not overly browned.
08 -
Allow to cool slightly on the baking sheet before serving warm.