Step 1

Prepare two pans: the first pan will be an 8x8 inch square baking pan. Line it with parchment paper, leaving some hanging over the sides. This makes it easier to remove the brownies later. Prepare a second pan, either a 9x5 or 8x4 loaf pan. Line it with parchment paper. Preheat the oven to 350°F.(See notes if you'd like to make the brownies without the crumbled brownie layer on top)

Step 2

In a large microwave-safe bowl (or over the stove), melt the butter. Add in brown sugar and granulated sugar. Whisk until the mixture pulls away from the sides of the bowl as you whisk, like a paste.

Step 3

Whisk in the eggs and vanilla extract. Add flour, salt, and cocoa powder, then whisk until combined (do not over-mix!).

Step 4

Add two thirds of the brownie batter into the prepared 8x8 pan. Pour the remaining one third of the batter into the second pan (loaf pan). Bake both pans of brownies at the same time for 27-36 minute. To know when they're ready, insert a toothpick inserted in the middle of each pan - it should come out with a few wet crumbs on it when its ready (not covered in wet batter, but not completely clean).

Step 5

Remove the pans from the oven, but leave the oven on. Set the loaf pan aside. Pour mini marshmallows evenly on top of the brownies in the larger square baking pan and put them back in the oven for another 4-8 minutes, or until the marshmallows look gooey and have started to turn a light golden brown. Meanwhile, use a spoon to break up the brownies in the loaf pan into chunks or small pieces. Careful, they will still be hot!

Step 6

Remove the marshmallow brownies from the oven. Take small chunks of crumbled up brownie from the loaf pan and sprinkle over top of the marshmallow layer, gently pushing them into the marshmallows. Repeat with all the crumbled up brownie pieces, then evenly sprinkle with chocolate chips.

Step 7

Let cool before removing from the pan and slicing.