A peanut butter sandwich (sometimes a peanut butter and jelly sandwich) was a Human sandwich food consisting of peanut butter between two slices of bread. Often, it would also feature a jelly of some sort.
Jonathan Archer explained that the Chef of the Enterprise NX-01 was able to prepare anything from a peanut butter and jelly sandwich to turkey "with all the trimmings" when asked by Liam Brennan. (ENT: "Breaking the Ice")
A ferengi was apparently eating a peanut butter and jelly sandwich retrieved from the mess hall at Captain Archer's request for food. (ENT: "Acquisition")
In 2376, Captain Janeway prepared pot roast when she invited Lyndsay Ballard to dinner in the Captain's quarters, however her infamous replicator liquefied the pot roast and they were forced to eat peanut butter sandwiches. Ballard didn't mind too much, stating that she had lived on them at Starfleet Academy. (VOY: "Ashes to Ashes")
In 2377, Tom Paris made peanut butter toast for his wife, B'Elanna Torres, but she could not eat it in time, because she had an appointment in sickbay with The Doctor regarding her pregnancy. (VOY: "Lineage")
Later that year, during a meal prepared by Seven of Nine, she offered to replicate a peanut butter and jelly sandwich for Paris when he asked for salt for the quail that she had prepared. (VOY: "The Void")