Mashed potatoes can be made almost completely ahead. Do nearly everything – boil, peel and mash; stir in milk and salt – up to two days ahead. Before serving, reheat. Adding butter at the last minute makes them taste freshly mashed.
I discovered this excellent Thanksgiving gravy recipe years ago! It is gravy that, unlike most, can be made AHEAD of time. The gravy will keep for 3 months when frozen in an airtight container.