I found this recipe on the Cooks Illustrated website and it is very good! Bringing the butter, peanut butter, and eggs to room temperature makes it easier to blend the ingredients. Be sure to grind the peanuts, since whole, and even chopped peanuts tend to slip out of the dough. If using unsalted butter, increase salt to 1 teaspoon. Keep finished cookies refrigerated in airtight container. To restore just-baked chewiness, wrap a cookie in a sheet of paper towel and microwave for approximately 25 seconds. Cool before serving.