Ingredients
¾cupunsalted butter,(1.5 sticks), softened to room temperature
¾cuplight brown sugar,or dark, packed
¼cupgranulated sugar
1large egg,at room temperature
2tsppure vanilla extract
2cupsall-purpose flour,spoon and leveled
2tspcornstarch
1tspbaking soda
½tspsalt
1¼cupsemi-sweet chocolate chips
12regular marshmallows,cut in half
4ozsemi-sweet chocolate bar,finely chopped
⅓cupgraham cracker crumbs,crushed
Preparation
In a large bowl using a hand-held mixer or stand mixer with paddle attachment, beat the butter, brown sugar, and granulated sugar together on medium speed until creamy, about 2 minutes. Beat in the egg and vanilla extract. Scrape down the sides and bottom of the bowl as needed.
In a separate bowl, combine flour, cornstarch, baking soda and salt. Pour dry ingredients into the wet ingredients, then beat on low speed until combined. The cookie dough will be slightly thick. On low speed, beat in the chocolate chips. Cover dough tightly with aluminum foil or plastic wrap and chill for at least 1 hour and up to 2 days. Chilling is mandatory for this cookie dough.
Remove cookie dough from the refrigerator and allow to sit at room temperature for 10 minutes. Preheat oven to 350 degrees F then line 2 large baking sheets with parchment paper or silicone baking mats; set aside.
Once chilled, the dough will be slightly crumbly, but will come together when you work the dough with your hands. Roll balls of dough, about 1.5 tablespoons of dough each, into balls.
Bake for about 10 to 11 minutes, until barely golden brown around the edges. The cookies will look extremely soft when you remove them from the oven.
Turn the oven up to high broil. (If the oven gets overly hot on high, turn on a low broil.)
Top each cookie with a marshmallow half, sticky side of the marshmallow down on the cookie. Return to the oven for only 1 to 2 minutes or until the broil setting lightly toasts the marshmallow. Keep a very close eye on it as it toasts fast!
Remove cookies from the oven and cool for about 5 minutes on the cookie sheet as you prepare the chocolate. Using the back of a spoon, press the marshmallow down if it didn’t melt on its own. (Sometimes it holds its taller shape, but gently pressing down flattens it out.)
Place the chopped chocolate in a medium heat-proof bowl. Melt in 20-second increments in the microwave, stirring after each increment until completely melted and smooth. Spoon evenly over the marshmallow. Top with graham cracker crumbs.
Allow chocolate to completely set at room temperature for about 60 minutes, or in the refrigerator for about 30 minutes.
