25 minutes in when I added the marshmallows
And this is the mushy mess I was left with after another 20 minutes in the oven.
Lessons I learned: Tinfoil in my pan made cleanup a whole bunch easier. I won't however be putting tinfoil in the pan next time I do brownies, when I did attempt cutting them I ended up with all kinds of little bits of foil stuck in my food. Also this idea probably would have worked out much better if I had used mini marshmallows - and not too many of them! My favorite learning experience from this though was that ooey gooey brownie marshmallowy mush tastes fantastic when warm and eaten with a spoon with some creamy vanilla ice cream!