Instructions

1. Preheat the oven to 350°F. Line a 8 x 8-inch square baking pan with parchment paper on all sides. Set aside.
2. In a large mixing bowl, whisk together the melted butter and brown sugar until combined. Whisk in the egg and vanilla and mix until glossy and smooth.
3. Add the flour, graham cracker crumbs, baking powder, salt and cinnamon if using. Use a silicone spatula to fold the batter until combined and no streaks of flour remain.
4. Transfer half of the batter into the prepared pan, using a silicone spatula or your fingers to push it evenly to the edges. The layer will be thin, but this is correct! 
5. Spread the fluff all over the bottom layer, using a greased silicone spatula to push it into an even layer. Form balls with the remaining blondie dough, pressing it between your palms into flat discs and placing all over the top of the fluff to almost completely cover it. It’s okay if there are a few small holes poking through. Gently press the Hershey chocolate pieces into the top of the blondies.
6. Bake until the blondies are golden brown and feel firm to the touch, 20 to 25 minutes. Place the pan on a cooling rack and allow the blondies to cool slightly in the pan before removing and slicing!