Watercress sandwich
From Memory Alpha, the free Star Trek reference.
A watercress sandwiches is a type of Earth sandwich food made with bread and watercress.
When Admiral Alynna Nechayev beamed aboard the USS Enterprise-D in 2370, Captain Jean-Luc Picard prepared a plate of Bularian canapés, watercress sandwiches and a pot of Earl Grey tea to make the Admiral feel welcome aboard the Enterprise. (TNG: "Journey's End")
