Put the sugar and water into a saucepan, boil for 3 to 4 minutes over a moderate heat to make a syrup. Put the yolks into a mixing bowl placed in a hot, but not boiling, double boiler. Whisk to mix, still whipping (with an electrical whisk) pour in the boiling syrup, little by little like the oil of a mayonnaise. When the yolks have doubled in volume and are hot, remove the bowl from the hot water and keep whisking until cold. Then whip the cream, adding the vanilla sugar and the rum when beginning to stiffen. Mix thoroughly then combine with the egg yolks and add the grated coconut except 2 or 3 tablespoons which you will keep to sprinkle the cake with. Cover the sandwich tin with greaseproof paper with both sides oiled. Pour in the mixture, put into the freezer until firm under finger pressure, this takes about 4 hours. Turn out, remove the paper, coat with the grated coconut and keep the cake in the refrigerator, not in the freezer.
