Combine vinegar, juice, butter, and sugar in a 13- by 9-inch glass baking dish. Cut off top 3/4 inch of apples to make lids. Scoop out cores with a melon-ball cutter and replace lids. Put apples in baking dish and cover with foil. Bake in middle of oven until very tender but still intact, 1 to 1 1/4 hours.
Transfer apples to plates and boil pan juices with brandy in a saucepan until reduced to about 1 cup. Fill apples with crme fraîche and serve with sauce.
