mashed potatoes

from The Collaborative International Dictionary of English v.0.48

mashed potatoes \mashed potatoes\, n. pl.
   Potatoes which have been boiled and mashed to a pulpy
   consistency, usu. with sparing addition of milk, salt,
   butter, or other flavoring. It is a popular accompaniment to
   a meat course [U.S., 1900's], providing bulk and calories to
   a meal.
   [PJC]