After unmoulding it, make the glassa fondente. Mix the icing sugar and a little bit of water in a small pot. I made this for the first time, so I did not manage to measure the exact amount of water needed, but the glaze needs to be smooth, fluid and “creamy” and still be white. If you put too much water, it will not be thick enough to cover the sponge cake! And if you put too little water, it will not be smooth! So, I suggest you look at the glaze in the picture and add water little by little (it is easier to add than to remove!). After you mix it well, put the pot on the fire and bring to a simmer (keep stirring!). As soon as it starts simmering, put the fire off and pour it over the top of the cassata.