Design Eat Repeat

0 Preheat oven to 350°F.
17 Two notes before starting! (1) Note that this is a thicker dough that is easiest to make with a stand mixer. If you only have a handheld mixer, you may just need to use a spatula to help mix the flour in. (2) I created an interactive slideshow of me talking through all my tips & tricks to make these – I recommend tapping through this before you make them!
1 In a large bowl, use an electric mixer on medium-high speed to cream softened unsalted butter [adjustable](¾ cup, 1 ½ sticks), light brown sugar (¾ cup), and granulated sugar (¾ cup)[/adjustable] for 2 minutes until light and fluffy.
2 Add the eggs [adjustable](2 large), vanilla extract (2 teaspoons), and light corn syrup (3 tablespoons)[/adjustable] and mix on low speed until combined. Scrape down the sides of the bowl so everything can combine.
3 Add in baking powder [adjustable](1 teaspoon) and salt (½ teaspoon)[/adjustable] and mix for another 5-10 seconds until combined.
4 Lastly, add dark cocoa powder [adjustable](¾ cup) and all-purpose flour (2 ¼ cups)[/adjustable] and mix on medium until combined.
5 Spray a light-colored metal 9×13 pan with cooking spray, then line pan with two pieces of parchment paper, leaving a 2-inch overhang on each long side so that you will be able to lift the bars out of the pan.
18 Line the bottom of the pan with graham crackers.
15 Drop the dough into small chunks in the pan. This will help disperse everything so that you can easily smooth it out. I highly recommend this method rather than trying to spread out a large chunk. Once all dough has been added, use a spatula or your hands to press down the dough into a smooth layer (being sure to get all the corners). Be careful not to shift around the graham crackers too much.Tip: This dough is a little sticky, so to help spread, I recommend spraying your hands with cookie spray or use place another piece of parchment paper on top and continue pressing down.
6 Bake bars at 350°F for 18-22 minutes, or until the center no longer looks wet. The center may look a tiny bit underdone but the bars will continue to bake in the hot pan when cooling.Immediately proceed to next step.
19 Right after your bars come out of the oven, top with the full 10-ounce bag of marshmallows. Turn on the “BROIL” function on your oven and place the pan on the bottom or middle rack.Stand by the oven and watch it very closely – do not walk away! When you start to notice a light brown, rotate the pan to avoid any hot spots. Remove from the oven when the marshmallows are golden brown.
20 If desired, press Hershey bar and graham cracker pieces into the top.
21 Before cutting, allow the pan to fully cool, then refrigerate for 30-60 minutes to help firm up the chocolate and marshmallows. This will give you the most clean cuts. Want to get super clean cuts? For this month's baking challenge, I've created a cool interactive slideshow with video tips on how to make these! Be sure to watch this for tips to cut the bars really cleanly!
16 Store in an airtight container or cover the pan with plastic wrap. If your kitchen is warm or you plan to serve these outdoors, keep referigerated until time to serve to help slow down the marshmallows and chocolate from getting too warm.