Cooking the blueberries in their juices really helps to bring out their flavour and creates a wonderful contrast with the smooth, rich custard in this dessert. With blueberries, you probably won’t need to use any additional sugar unless you have a very sweet tooth. If you decide to use fresh currants (black or red) instead, you may need a sprinkle. Figs, apricots and peaches will all work beautifully in baked custard, too.