Preheat the oven to 350F. Line a 8x8” or 9x9” square baking with parchment paper. Arrange the graham crackers on the bottom of the lined pan, breaking any graham crackers to fit. Set aside.

Add the butter to a saucepan over medium heat. Allow to melt and slightly brown, while stirring continuously (~5-8 minutes). The butter will start to foam and sizzle around the edges. Once some of the foam subsides, the milk solids at the bottom of the pan, turns brown and starts to smell toasty and nutty, remove from the heat.

Add in the chocolate chips, vanilla, and cocoa powder. Stir with a wooden spoon or spatula until the chocolate chips are melted and the mixture is smooth. You can return the pan to the heat if needed to help the chocolate chips melt. Set aside and let slightly cool.

In a large bowl, beat together the egg, egg yolks, and both sugar until well combined and frothy.

Add the chocolate mixture and sourdough discard, and beat on low until combined.

Then, add in the flour and salt, and stir with a wooden spoon or spatula until just combined (the batter is going to be VERY thick).

Optional: fold in additional chocolate chips.

Scoop and evenly spread the batter into the prepared pan with the graham crackers. Bake at 350F for 30 minutes.

After 30 minutes, remove the pan from the oven and pour the melted chocolate on top. Use a spatula to spread the chocolate over top the brownies.

Arrange the marshmallows on top in rows, and return the pan to the oven for 5 minutes.

Then, remove from the oven and toast the tops of the marshmallows with a kitchen torch OR by placing the pan on the top rack in the oven, and broiling for 15-30 seconds.

Allow to cool for 15-20 minutes before cutting into 16 squares.