ZamZ makes an attempt at a recipe node. But this one is simple enough even for me and it's kinda good for you.

Ingredients

Bread (sliced, white or brown, rolls, any sort really)
Banana (erm, possibly you guessed that bit)
Butter (unless you don't like butter, in which case skip this. Don't skip on the banana or the bread tho' or the whole Banana Sandwich thing kinda goes out the window)

Ok, put the butter on the bread. As much or as little as you want. Yeah, layer it out there, don't worry your little self about fat content here, the other ingredients are fruit and that makes up for any evil you do with the spreads.

Now, the tricky bit. Put the banana on the bread (over the butter, that is). Seems not too tricky, it's deceptive. The tricky bit is this, Don't Slice the Banana. Squidge it. Really like smear the thing around the bread. The polite in society will insist on slices of even thickness being evenly spread around the bread/butter combination. Ignore these fools. The whole joy of the banana sandwich experience is having to catch the squidged banana that comes out the opposite end you are biting into. It's messy. But so's ice-cream and that's fun.

What? You don't make a mess with ice-cream? Away! Ice-cream should not be eaten, it should be attacked. And so should this sandwich.