The Gourmet Cookbook via Joy the Baker (I made some small modifications to the directions, see below)
1 cup all-natural chunky or smooth peanut butter
1 cup sugar (1/2 cup brown sugar and 1/2 cup granulated sugar)
1 teaspoon baking soda
Preheat oven to 350 degrees F. Grease a baking sheet (I don't think I did this). Combine sugars, egg and peanut butter (it will seem runny at first) until well combined, about 2-3 minutes. Add baking soda and mix for another minute.
Roll into walnut sized balls and create a criss-cross pattern with a fork. (Baby O loved doing this!)
I added jelly to some of them, but I liked them best without the jelly.
Bake for 6-8 minutes (Joy cooks them for 10 minutes, but I like my cookies on the gooey/soft side), until lightly browned.
Enjoy! Note - they do break apart easily, but since I undercooked them a little, they mostly stayed together.