Place all of the well-scrubbed potatoes in a 3-quart saucepan. Cover with cold water and bring to a boil over high heat. Reduce heat to a simmer and cook until potatoes are very soft, about 20-30 minutes. Drain and when cool enough to handle, peel. In medium bowl, combine potatoes, butter, brown sugar and nutmeg. Using a potato masher, cream the potatotes until very smooth. In small bowl, beat eggs, 1 cup evaporated milk and vanilla together. Beat this mixture into the potatoes. Mix thoroughly. Pour into piecrust and drizzle the remaining 1/4 cup of milk on top. Bake 15 minutes in a preheated 450~ oven then turn heat to 325~ and continue baking for 30 minutes or more until the filling is set.