Put butter in small saucepan and pour on water. As soon as water again reaches boiling point, add flour all at once, and stir until mixture leaves sides of saucepan, cleaving to spoon. Remove from fire and add eggs unbeaten, one at a time, beating mixture thoroughly between addition of eggs. Drop by spoonfuls and fry in deep fat until well puffed and browned. Drain, make an opening, and fill with preserve or marmalade. Sprinkle with powdered sugar and serve on a folded napkin.