Place yams into a large pot and cover with salted water. Bring to a boil, then reduce heat to medium-low, cover, and simmer until tender, about 20 minutes.
Drain and allow to steam dry for a minute or two.
Preheat oven to 325 degrees F (165 degrees C).
Return yams to the cooking pot, and mash with juice until smooth. Pack mashed yams into a 3 quart casserole dish, dot with butter, then sprinkle with brown sugar and nuts. Loosely cover with aluminum foil.
Bake in preheated oven until hot and bubbly, 35 to 40 minutes.
