I remember standing on a stool watching my Gram make this for her famous brownies, and after waiting what seemed like a century for it to cool down, lucky me always got to lick the spoon! Birthday rules prevail though - if it's your birthday, you get to lick the whisk and clean out the pan!
The fudge will start to set as soon as you get it poured out of the pan - so give it a quick swirl with an offset spatula if you want to smooth or twirl the top at all, sprinkle with your favorite sprinkles, and then just wait patiently. The fudge frosting will thicken as it cools and doesn't require any other attention. So simple, and so wonderful!
Gotta run - they're fighting over the pan right now!