In a large saucepan over medium heat, melt the butter until it’s golden and slightly nutty—hello, browned butter goodness! This step adds a rich, toasty flavor that sets these treats apart.
Add 10 ounces of the marshmallows to the saucepan and stir until they’ve completely melted into the butter. The combination of butter and marshmallows is basically edible glue for all the magic about to happen.
Pour in the sweetened condensed milk and stir until everything is velvety smooth. This adds a creamy richness that takes these bars to the next level.
Remove the pan from the heat and fold in your honey graham cereal. Stir gently but thoroughly until every piece is coated in the sticky marshmallow mixture.
Toss in 5 more ounces of marshmallows and 10 of the mini Hershey’s chocolate bars, broken into pieces. Fold them into the mix so you get gooey marshmallow pockets and melty chocolate in every bite.
Grab a 9x11 baking dish and butter it up (literally). Press the cereal mixture into the dish, spreading it out evenly. Don’t press too hard—you want them to stay nice and fluffy.
Sprinkle the remaining marshmallows and chocolate pieces on top for that picture-perfect s'mores look.
Cover the dish and pop it into the refrigerator for at least 30 minutes. Once the bars are set, they’re ready to cut and devour.