Preheat oven to 325 degrees. In a medium sized bowl, mix all three ingredients together. This will form a thick cookie dough. Roll dough into balls about an inch and a half in diameter and place them on an ungreased cookie sheet about two inches apart. Using a fork press down lightly on the cookies to make a criss-cross pattern on top. If you want to decorate, sprinkle on a little colored sugar. Bake cookies until golden brown. Allow to cool for ten minutes and serve. As a side note, make sure the peanut butter is fresh or the cookies will turn out tough.