Peanut butter was a Human food that was made by grinding peanuts into a creamy texture, and usually sweetened.
According to Doctor Phlox, Malcolm Reed had the odd habit of spreading peanut butter on his pancakes. (ENT: "Silent Enemy")
Neelix learned to make peanut butter and jelly sandwiches for Tom Paris who considered the snack "comfort food". (VOY: "Faces")
In 2376, Captain Janeway attempted to prepare pot roast but the replicator liquefied the pot roast and they were forced to eat peanut butter sandwiches. (VOY: "Ashes to Ashes")