01 -
Preheat oven to 350°F. Line a metal 9x9-inch pan with parchment paper. Use half of the graham crackers to line the bottom of the pan.
02 -
Melt 18 tablespoons (1 cup + 2 tablespoons) salted butter in a microwave-safe bowl in 30-second increments until melted. Pour the melted butter into a large mixing bowl. Whisk in sugar by hand until smooth, about 30 seconds.
03 -
Add eggs and vanilla extract to the mixture and whisk for 1 minute. Whisk in melted chocolate chips until combined and smooth.
04 -
Use a rubber spatula to stir in flour, cocoa powder, and salt until just combined.
05 -
Pour the batter over the graham crackers in the prepared pan and smooth the top.
06 -
Bake in the preheated oven for 30-35 minutes until brownies are cooked through.
07 -
While brownies bake, break the remaining graham crackers into small pieces. Break the chocolate bars into small pieces as well.
08 -
Remove the brownies from the oven and sprinkle graham cracker pieces, chocolate pieces, and mini marshmallows over the top.
09 -
Return the pan to the oven approximately 8 inches under the broiler element. Broil, watching closely, until the marshmallows are browned, about 2 minutes.