Grease a 9"x13" baking dish with butter or neutral oil. Then line with a parchment paper sling or just the bottom.
In a large 5-8 qt. pot add butter over a medium heat. Melt the butter until completely melted. Then keep stirring as the butter browns - from melted, to dark golden, to a brown and nutty fragranced mixture. This usually takes about 4-6 minutes in total. You don't want it to burn, so keep a close eye on it. Mix in salt.
Slowly stir in marshmallows about 1 cup at a time until incorporated well. I use a wooden spoon as it's sturdiest.
Turn off heat and mix in the cereal, about ½-1 cup at a time.
Add in 1 tablespoon of sprinkles at a time (2 tablespoon) until all ingredients are incorporated.
Scoop mixture into the prepared baking dish and push down mixture until it has a flattened surface (can use hands, spoon, or bottom of a cup – greasing it makes it easier to use). Top with remaining 1 tablespoon of sprinkles and the googly eye sprinkles.
Let cool, remove from pan, slice, and enjoy!
Notes
Marshmallows – I do suggest a few things for these. One, I suggest using mini-sized marshmallows. I find these easier to melt into the butter quicker. I also suggest using marshmallows with gelatin. I’ve yet to find a vegan marshmallow that truly melts into the butter.
Unsalted Butter – Yes! Always use unsalted butter in baking. This allows you to control the amount of salt added to the treats.
Brown Butter – it should give off a nutty smell and be fairly dark. Just be sure to keep your eyes on it to make sure it doesn't burn.
Parchment Sling – try using a parchment sling to pop the treats out and cut them on a cutting board.