We make a lemon ice which would adapt very well to orange.
250g sugar
250ml water
Heat the water and dissolve the sugar to make a 1:1 syrup. Allow to cool.
Wash and scrub several citrus (no need to scrub if unwaxed) and grate the zest.
Squeeze enough citrus to give 250-300ml juice. Remove the pips, but we leave in any bits of pulp.
Mix syrup and juice and taste for sweetness. Sometimes you need a little more sugar for lemon, but I doubt you'll need more for orange.
Mix in the grated zest. Put into the freezer to get very cold, but don't let it start to freeze.
Whip two egg whites until frothy and starting to peak. Fold the egg whites into the now very cold fruit syrup. If you have an icecream maker, put it into that. If not, pour into a suitable container and put into the freezer. Set the freezer to "continuous" or similar setting.
Check it after an hour and then every half hour. When a layer has frozen on the bottom and sides of the dish, scrape the frozen layer off and into the middle. Repeat this until the whole thing has begun to get thick. Then put a lid on and allow to freeze completely.
The egg white makes a much lighter yet richer dessert than a simple sorbet or granita. If your guests are squeamish about "raw" egg, don't tell 'em.
