Prepare and bake 1 package brownie mix according to directions. Immediately on removing from oven, sprinkle 2 cups miniature marshmallows and 6 ounces of chocolate chips over warm brownie surface and return to hot oven for about 2 minutes to melt.
Arrange graham crackers on top of the hot marshmallows and press. Cool completely and cut into servings along graham cracker indentations.