Prepare the brownie mix just like the package tells you to. Once those brownies come out of the oven, while they’re still nice and hot, spread the marshmallows evenly over the top. Now, pop the brownies back into the oven (that’s already turned off, by the way) and let the marshmallows puff up for about 2-3 minutes. Keep an eye on them so they don’t exaggerate it!
While the marshmallows are doing their thing, grab a medium saucepan and combine the half-and-half, butter, and sugar. Bring it to a boil, but keep stirring to make sure nothing sticks or burns at the bottom. After about a minute, toss in the chocolate chips. Keep stirring until they’ve completely melted into a smooth, rich frosting. As soon as it’s ready, spread that delicious chocolate frosting all over the marshmallow-topped brownies.
