Preheat oven to 350 degrees F. Grease a 9x13-inch baking dish. Set aside.

Crush the graham crackers into fine crumbs. Stir in melted butter and sugar until crumbs are well moistened. Press the crust mixture into the bottom of the greased pan. Use a measuring cup or a glass to press the crumbs down.

Bake the crust for 10 minutes.

In a small microwave-safe bowl, combine 6 oz unsweetened chocolate and 1/2 cup butter. Microwave on high power for 30 seconds then stir well. Continue heating in 30-second intervals then stirring until chocolate is fully melted and mixture is smooth. Set aside.

In a medium bowl, whisk together eggs, sugar, salt, and flour until combined. Stir in chocolate mixture and vanilla extract. Pour into prepared pan.

Bake 25-30 minutes then remove from the oven and top with miniature marshmallows and pieces of Hershey's chocolate bars.

Place the brownies back into the oven for 8 minutes or until marshmallows are toasted and chocolate is soft.

Cool completely before slicing.