1 cup peanut butter
1 cup brown sugar
1 egg
That is the original recipe in it's entirety, but I've always added 1/2 cup oatmeal to bulk it up a bit and add some texture. This is the only thing I think I've ever cooked that I don't need instructions for!
Bake at 350 for 8-10 minutes (mine have always taken more like 11-13, probably due in part to the extra ingredient and also the fact that I make big, fat cookies!).
Makes about two dozen small or 18 large cookies.
Give them a try!
*and possibly the best, you be the judge