I just got a food processor and I want to try to make my own peanut butter. I know it's pretty simple - peanuts, salt, and maybe oil, but I do not know the quantities. Does anyone have experience making nut butters? I know it'd probably taste better if I bought peanuts in the shell and roasted them myself, but what I have is roasted peanuts that are "lightly salted". What amounts should I use to make good homemade peanut butter?