1 cup unsalted butter, softened
½ cup packed dark brown sugar
1 cup granulated sugar
2 tsp. vanilla
2 2/3 cups all-purpose flour
2 tsp. baking powder
3/4 tsp. kosher salt
1 ½ cup graham cracker crumbs
4 Hershey chocolate bars (4.4 oz. each)
3 cups marshmallow fluff (16 oz. container) -- and don't forget to spray that spatula when you're putting this on!
Preheat oven to 350 degrees F. In a large mixing bowl, beat butter with sugars; add egg and vanilla and beat until light and fluffy. In a separate mixing bowl, combine dry ingredients with graham cracker crumbs; add to butter mixture and mix until well combined.
Grease a 9 x 13 baking dish with nonstick spray and line it with parchment paper, so the paper hangs out over the ends a little. (These will be your handles for lifting the bars out of the pan after you bake – very important!) Divide dough in half and press one half across the bottom of prepared 9 x 13 baking dish.
Place 3 chocolate bars over dough layer, side by side, then cut remaining chocolate bar into 4 lengthwise strips. Place these chocolate strips into the open areas around edges of chocolate bars already in the baking dish, on the end and at the top and bottom. Spread marshmallow fluff over chocolate bars, making sure to touch the edges on all sides of baking dish. Crumble the remaining half of dough into small pieces over marshmallow fluff; pat down gently after crumbling. Place baking dish into oven and bake for 30-35 minutes or until golden brown and puffed. Cool completely before cutting into bars.
**Once smores bars are cooled to room temperature, place into refrigeration for 3-4 hours; after smores bars are chilled, they are much easier to cut. Then, if desired, warm bars in the microwave to make ooey-gooey once again – total yum! Use parchment paper to remove smores from pan and place onto a large cutting board. A bench scraper is ideal for cutting into bars.