Pre-heat the oven to 350 degrees F. Grease a 7" x 11" baking pan.
In a medium bowl, mix together the graham cracker crumbs, sugar, melted butter, and salt. Pour into the baking pan and press firmly down on the bottom. Bake for 8 minutes.
In the same bowl mix together the flour and baking soda.
In a glass or microwaveable safe bowl, microwave one cup of the chocolate chips and butter at 50% power for 3 minutes, and stir. Let cool for 5 minutes.
In a large bowl whisk the eggs. Add the sugar, cocoa powder, vanilla, and melted chocolate mixture to the bowl. Mix until combined. Add the flour mixture and mix until combined. Pour over the cooked graham cracker crust.
Bake for 30 minutes and let cool for at least 20 minutes. Sprinkle the top with 1/2 cup of chocolate chips.
Spread out the mini marshmallows ontop of the cooked brownies. Broil on high for 30-60 seconds. Let cool compltly before cutting.