Start the Cookie Dough: Melt the butter in a large mixing bowl. Whisk in the sugars until well combined, about 30-60 seconds. Add the eggs and vanilla, and whisk until smooth and combined, about 30-45 seconds.
14 and 1/2 tbsp salted butter, melted, 3/4 cup dark brown sugar, packed, 3/4 cup granulated sugar , 2 large eggs, at room temperature , 1 and 1/2 tsp vanilla extract
Finish the Cookie Dough: Stir in the dry ingredients, then the hershey's pieces, chocolate chips, and graham cracker crumbs.
2 and 2/3 cups all-purpose flour, spooned & leveled or weighed out , 1 tsp baking powder, 1 tsp baking soda, 1/2 tsp salt, 3 full-size hershey's chocolate bars, roughly chopped, 1 and 1/3 cups semi-sweet chocolate chips, 8 whole graham crackers, crushed*
Scoop & Stuff the Cookies: Place the extra graham cracker crumbs (from the "assembling" part of ingredients above) onto a small plate. Scoop dough into balls 55 grams in size. Flatten each dough ball, then place a marshmallow in the center of each and encase the marshmallow in the dough so just a bit is peeking out at the top. Then, roll each dough ball in the graham cracker crumbs (around the sides, not over the mallow). Pre-heat your oven to 365℉. Line a few cookie sheets with parchment paper. 24 full size marshmallows, 3 whole graham crackers, crushed into fine crumbs
Chill Cookies: Chill the stuffed cookies in the freezer for 30 minutes - the dough needs to feel solid. I highly recommend freezing these instead of chilling in the fridge - this will help prevent the marshmallows from dissolving while the cookies bake. Some readers have said that using vegan marshmallows helps as well.
Bake: Place about 5 cookies on a sheet (leaving the rest in the freezer). Bake for 8-10 minutes. The edges will appear *just* set and the cookies will almost seem like they need a minute more - this is the perfect time to pull them out! They will set up to the perfect soft-baked consistency as they cool. See note below.Immediately place a round cutter around the outside of each cookie and swirl the cookie within it to "scoot" them into perfect circles. (Some of the cookies will go a bit wonky in the oven - this is normal!) This also helps them appear thicker. You can also pop a few extra chocolate pieces onto any bare spots on top of the cookie to make them look fancy. Note: The marshmallows will be light golden brown, or they may not be very brown at all - you can use a kitchen torch to toast the mallow centers a bit further after the cookies are baked! extra chocolate chips, for "touch-ups"
Serve & Store: Let cookies cool on the baking sheet on a cooling rack for 5-15 minutes before digging in to the warm gooey goodness. Store cooled cookies in an airtight container at room temperature for 3-4 days.