The white chocolate sauce adds an accent of richness and sweetness without cloying. Fresh berries look wonderful with this, too. Produce is more variable than just about anything else, so you may have to vary the amount of sugar called for here. Stir it in well to dissolve, then taste a bit of the mixture. If it is not sweet enough, simply add a bit more sugar, stir in, and taste again.
Superfine sugar is used here, as it dissolves almost instantly.
You can buy it in supermarkets in a one-pound box, or make your own by processing sugar in a food processor fitted with a steel blade until the sugar grains are extremely fine. You'll need an ice cream freezer of one-quart capacity to make this. As with all homemade frozen desserts, the sorbet should be eaten within 2-3 days of churning. Incidentally, if you've never worked with a mango before, the fruit is ripe when it yields to gentle pressure. The pit clings to the flesh and must be cut away, and the skin must also be discarded.