Remove stalks and put the washed greengages into the pan with the water. Stew slowly until the fruit is well broken down. Ripe fruit or very juicy varieties will need only a small quantity of water and will be cooked in a few minutes. Firmer varieties may take about 20 min. to break down, and will need the larger quantity of water. Add the sugar, stir over a low heat till dissolved, then boil rapidly, removing the stones as they rise to the surface (a stone basket clipped to the side of the pan is useful for holding the stones, and allows any liquid to drip back into the pan). Keep testing for setting point after about 10 min. rapid boiling. Skim, pot and cover.