- 1 package brownie mix (~14 ounce pack)
- ½ cup butter
- ¼ cup avocado oil (or any neutral oil)
- 1 large egg
- 1 cup sourdough starter discard
- 3 tablespoons water
- 2–3 cups crushed graham crackers
- 1 ½ cups miniature marshmallows* (see notes)
- 1 milk chocolate bar, coarsely chopped
- ¼ cup dark chocolate chips
- Brown the butter in a small saucepan until bubbly, and dark golden to light brown. Stir it continuously, careful not to burn it. Remove from heat and allow the butter to cool to room temperature, but still liquid.
- Gather the other ingredients and preheat the oven to 350 degrees F.
- Grease a 8×8-inch baking dish with a little cold butter, or line it with parchment paper.
- Crumble enough graham crackers to line the bottom of the pan in an even layer. Leave the rest for topping.
- Stir together the brown butter, oil, egg, water, and sourdough starter in a medium bowl until well blended.
- Add in the brownie mix and stir until combined.
- Pour batter into the prepared pan.
- Bake in the preheated oven for about 35 minutes.
- While the brownies are baking, make the topping. Break graham crackers into small pieces and place into a bowl. Add marshmallows and chopped chocolate and toss to combine.
- Once they’re fully baked, remove brownies from the oven, and turn the oven to broil. (adjust your oven rack if necessary, you don’t want the brownies too close to the top heating element; center of the oven is best.)
- Sprinkle the topping ingredients over the brownies.
- Return brownies with the toppings to the oven and broil for 2 minutes until the marshmallows are just toasted. Don’t broil too long or you will burn the chocolate!
- Let cool for about 5 minutes, then slice into 12 squares and enjoy.
