120ggraham crackers(about 1 cup/8 graham crackers)
50gbrown sugar(¼ cup/1.75 oz)
95gbutter(6¾ Tbsp/3.3 oz)
Brownie Layer
227gbutter(8 oz/1 cup/2 sticks)
60gdark chocolate(2 oz) - 60-70%
60gdutch-processed cocoa powder(2 oz/¾ cup)
1½teaspoonespresso powder(optional)
400gsugar(14 oz/2 cups)
3eggsroom temperature
1teaspoonvanilla extract
½teaspoonfine grain salt
125gall-purpose flour
35gbaking chocolate chunks(¼ cup/1.25 oz)
Topping
226gmarshmallows(8 oz, about half a 16-oz bag)
35gbaking chocolate chunks(¼ cup/1.25 oz)
Instructions
Make the Graham Streusel
Crush the graham crackers, either in a food processor or in between layers of parchment paper with a rolling pin. Add to a bowl if you used the rolling pin method.
Add the sugar to the graham cracker crumbs and mix well (or pulse in the food processor).
Melt the butter in a small saucepan or in the microwave and pour it on top of the graham mixture.
Mix by hand or pulse in the food processor until it fully incorporates and will clump together when pinched. You can make this ahead and store it in the fridge for up to a week. (Try not to snack on it!)
Make the Brownie Batter
Preheat the oven to 350°F (177°C/gas mark 4).
Prepare a 9"x13" baking tray by spraying it with baking spray and lining it with parchment paper, letting the edges of the parchment stick up over the sides of a pan so you can use it as a sling to remove the brownies from the pan later.
Melt the butter and chocolate together in a heat safe bowl over a water bath, or in a microwave safe bowl in the microwave. Run the microwave in 10 to 15 second bursts, mixing with a spatula each time the microwave stops.
Add in the cocoa powder and mix well until combined. You can do the mixing in a stand mixer, with an electric hand mixer or by hand.
Add the sugar, salt and vanilla extract and mix until combined.
Add the eggs one at a time and mix until combined.
A little at a time, add the flour. Gently mix until all the flour is just incorporated.
Fold in the 35 g of chocolate baking chunks.
Spread the batter out evenly in the bottom of the pan.
Top with Streusel and Bake
With your fingers, take a large pinch of the prepared graham cracker streusel and roll it until you get a large crumb that sticks together. Place the large crumb on top of the brownie batter and repeat until you've covered most of the batter.
Bake for about 35-37 minutes. You can start checking about 5 minutes before that. It will be done when the internal temperature reaches 205°F (96°C).
Add Marshmallows and Chocolate
Place the marshmallows on top while it is still warm and sprinkle the chocolate chunks over the top as well.
Turn on the broiler to a low setting and place the baking tray under the broiler. Keep an eye on it as it should not take very long to start melting and toasting the marshmallows.
When the marshmallows are toasted to your liking, remove the tray from the oven and let the brownies cool in the pan.
Serve and Store
Use the parchment or foil sling to pull the brownies up and out of the pan and move them to a cutting board. Cut them up into 12 large pieces, about 3" per side. (You might want to cut them smaller, though, because they are super rich!) If you are having trouble getting them out of the pan, you can either cut them directly in the pan or refrigerate them so they firm up.
You can store these in an airtight container for a week, or wrap individual brownies and freeze.