We gace Yasin apeanut butter sandwich when he was 2. He loved it and had no problems.
Imran started himself on peanut butter sandwiches by nicking Yasin's when he was a bit older than a year.
I decided after that to keep feeding him peanut butter although it was long before the recomened time because an allergic reaction is the immune system having a spack attack over the wrong thing and it's thought to be the frequent exposure to trace amounts of peanuts that makes it such a comon allergen so once he'd had it I though that full exposure was the best path to follow. So far no issues.