• Preheat oven to 325°F. Line a 9x9 baking pan with parchment paper, set aside.

For the graham cracker crust

• Prepare graham cracker crust by combining graham cracker crumbs, brown sugar and melted butter and stir very well to distribute all ingredients evenly. Press the mixture very firmly on the bottom of prepared baking pan. Set aside.

For the brownies

• Place butter, cocoa and sugar in a large microwave-safe bowl and microwave for about 1 minute and 30 seconds, or until butter is melted. Mix everything together until smooth. Add in eggs and vanilla and mix until smooth. Pour in the flour and mix until just combined. Then, mix some more until smooth and somewhat glossy. The batter will be very thick.
• Pour the batter on top of graham cracker crust and smooth it out into an even layer. Bake for 25-28 minutes or until a toothpick comes out with a small amount of batter on the bottom - this is what keeps them fudgy.
• Once brownies are done, pull them out of the oven and switch the oven to broil. Scatter mini marshmallows and chocolate chips on top. Place pan back in the oven under the broiler to lightly brown the marshmallows. Watch carefully.
• Allow the brownies cool for about 20 minutes before cutting into them.