01 -
Slice the marshmallows in half and place them in the freezer while you prepare the dough.
02 -
Preheat the oven to 375°F. Line two baking sheets with parchment paper and set aside.
03 -
In the bowl of a stand mixer with the paddle attachment, mix the cold butter, brown sugar, and granulated sugar on low speed. Gradually increase speed and cream together for about 4 minutes until pale and fluffy. Scrape down the sides of the bowl.
04 -
Add the egg and egg yolk, one at a time, mixing in between additions. Scrape down the bowl, then add the vanilla extract.
05 -
In a separate bowl, whisk together the flour, baking soda, cornstarch, and salt.
06 -
Add the dry ingredients to the wet mixture in two additions. Mix on low speed until just combined. Avoid over-mixing.
07 -
Add the graham cracker crumbs and chocolate chips. Use a large spatula or wooden spoon to mix until just combined.
08 -
Divide the dough into 2-ounce balls using a large scoop. Place them on a parchment-lined baking sheet, spaced 2 to 3 inches apart. Use your thumb or a tablespoon to make a well in the center of each ball. Insert half a marshmallow into each well and place 2 or 3 caramel pieces around it. Pull the dough over the fillings to enclose them, then roll into smooth balls.
09 -
Bake on the center rack for 9 to 10 minutes, until edges are set and golden. Centers should remain puffy and slightly underbaked.
10 -
Cool cookies on the baking sheet for 5 to 10 minutes before transferring to a rack to finish cooling.