In a small saucepan, boil apple cider over high heat until reduced by half, about 7 minutes. Set aside.

Bring a large pot of lightly salted water to a boil over high heat. Add the yams and cook until tender, 30 to 40 minutes, depending on size. Drain well. Using a kitchen towel to protect your hands, peel the yams and return to a warm pot. Add the reduced apple cider, butter, brown sugar and salt. Mash until well blended.

Serve hot.

Marshmallow varient
Spread half of the hot yams in a buttered 9x13-inch casseerole. Sprinkle with 1 1/2 cups miniatue marshmallows. Top with remaining yams. Bake in a preheated 350˚F oven for 20 minutes. Sprinkle the top with another 1 1/2 cups marshmallows. Broil in a preheated broiler, about 4 inches away from the source of heat, until the marshmallows are lightly browned, about 1 minute. Serve right away, 

Note: Can be prepared up to 8 hours ahead, cooled, covered tightly with plastic wrap and refrigerated. To reheat, place in a buttered 9 x 13-inch baking dish. Cover loosely with aluminum foil and bake in preheated oven at 350˚F until heated through, about 30 minutes.