¾cup1 ½ sticks unsalted butter, melted & cooled 5 minutes*
¾cuppacked light brown sugar
1large egg + 1 egg yolk, at room temperature
2tsppure vanilla extract
½cupsemi-sweet chocolate chips or chocolate chunks
1/4cupfinely crushed graham crackers
2Hershey’s chocolate bars, broken into pieces
coarse salt, for topping
Whisk the flour, baking soda, cornstarch, and salt together in a large bowl. Set aside.
In a medium bowl, whisk the melted butter, brown sugar, and granulated sugar together until smooth. Whisk in the egg and egg yolk. Finally, whisk in the vanilla extract.
Pour the wet ingredients into dry ingredients and mix together with a rubber spatula. Fold in the chocolate chips and crushed graham crackers.
Cover the dough tightly and chill in the refrigerator for at least 2–3 hours or up to 3 days.
Take the dough out of the refrigerator and allow it to slightly soften at room temperature for 10 minutes.
Preheat oven to 325°F. Line large baking sheets with parchment paper or silicone baking mats. Set aside.
Using a cookie scoop, portion out cookie dough, and place 12 on each cookie sheet. Flatten the cookies a bit with your hand and then press a few mini marshmallows and a piece of Hershey bar in each cookie. Top with a sprinkle of coarse sea salt.
Bake the cookies for 10–12 minutes or until the edges are very lightly browned. The centers will look very soft, but the cookies will continue to set as they cool. Cool on the baking sheet for 10 minutes.
After 10 minutes of cooling on the baking sheets, transfer cookies to a wire rack to cool completely.