Bake brownies according to recipe. Sprinkle marshmallows over brownies, while they are still warm, and cover with foil or a sheet pan. I have a silicone pan cover that I use. Here is a link for it.
https://www.pamperedchef.com/shop/Cook%27s+Tools/Cookware+Accessories/Large+Easy-Fit+Silicone+Cover/1271
In about 10 minutes the marshmallows will be warm and melty, like picture above.
Next spread out marshmallows.
Now the fun part! I used my kitchen torch to toast the marshmallows. If you don't have a torch then you can put your brownies under the broiler to toast them. Just keep a close eye on them because they will burn easily.
I have a few darker spots because I started the marshmallows on fire a few times. Oops 😁
I then decided to sprinkle some mini chocolate chips on top.
As the chocolate chips melted they started to sink into the marshmallows. As we were eating them I thought I could have also sprinkled graham cracker crumbs on these, yum! I guess I will save that for next time.