Makes 12 very rich brownies
For the Crust:
For the Brownie:
For the Topping:
Position a rack in the lower third of the oven and heat oven to 325 degrees F. Line an 8 by-8-inch square baking pan with foil so it hangs over both edges by at least one 1 inch.
To make the crust, lightly butter the foil with a wee bit of the melted butter. In a small/medium bowl, stir the rest of the melted butter together with the graham crumbs. Then add the sugar and salt and stir to combine. Press the crumb mixture evenly over the bottom of the pan. Bake until golden brown, about 20 minutes.
Meanwhile, make the brownie part. Put the butter and chocolate in a large microwave safe bowl. Melt in the microwave on medium percent power for 1-2 minutes. Stir, and microwave again until completely melted, about 2 minutes more. Remember that the chocolate will continue to melt after you remove it from the microwave and keep stirring. Don't let the chocolate burn! Stir into the melted chocolate/butter mixture both sugars and vanilla extract. Add the eggs and beat vigorously to make a thick and glossy batter. Add the flour and stir until just incorporated.
Pour batter into the prepared graham crust. Bake until the top is crispy and a toothpick inserted into the middle comes out mostly clean but with a few crumbs, about 50-55 minutes. Check the brownies after 45 minutes because oven temps do vary and this is a really thick layer of chocolate. Your batch may take even longer than 55 minutes. Our brownies took over an hour.
Remove from the oven and turn up the oven temp to 500 degrees Fahrenheit (do not use the broiler). Layer marshmallows across the top of the brownies. Put the pan back in the warmer oven on the middle rack and watch while the marshmallows toast. This will take 2-4 minutes. Remove them from the oven when they are a puffy, golden brown.
Cool on a rack, gently removing the brownies from the pan using the aluminum flaps. Carefully separate any marshmallow from the foil with a knife and peel away. Cut into 12 (2-inch-ish) squares while still warm (trust us, this is easier) and serve immediately.