Boil or bake the potatoes, peel and press through a very fine sieve, the finer the better. Add the yolks of three eggs, and beat well. Add the butter, beating well and thoroughly, and add the sugar and milk. Beat all very light, and add the whites of the eggs, beaten to a stiff froth. Mix thoroughly, add the grated nutmeg, ground spices, and blend well. Add finally, if desired, a wineglassful of good old Brandy or Whisky, and set the pan with the Potatoes in an oven and let bake for an hour. Place a brown paper on top for the first three-quarters of an hour, and take it off at the last quarter for the frangipane to brown nicely. Sprinkle with powdered white sugar. Serve hot or cold.