Jacked this from another anorexic recipe site that I found by mistake (seriously, I've searched for them on here and couldn't locate any before...). It's pretty dead now though.

"58 Calorie Vegan Mushroom Pizza

1 Portobello mushroom (20 calories)
garlic powder (optional)
1 spoon of pizza sauce (shouldn't exceed 10 calories)
vegan cheese (14 grams for 28 calories)

What you do:
Take the mushroom and wash it with a damp paper towel
Pull off the stem
Put a pinch of garlic powder on the underside of the mushroom (optional)
Add a spoon of tomato sauce
grate 14 grams worth of vegan cheese on it
broil for just under 10 minutes.

And there ya go, at not even 60 calorie pizza."