A peanut butter sandwich (sometimes a peanut butter and jelly sandwich when made with jelly) was a Human sandwich food consisting of peanut butter between two slices of bread.
In answer to young Liam Brennan's 2151 question about food on Enterprise NX-01, Jonathan Archer explained that the Chef of Enterprise NX-01 was able to prepare anything from a peanut butter and jelly sandwich to turkey "with all the trimmings". (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")
Neelix learned to make peanut butter and jelly sandwiches for Tom Paris who considered the snack to be "comfort food". (VOY: "Faces")
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")