- Warm the milk in a heavy-based saucepan with the orange zest until scalding hot. Meanwhile, put the whole egg, egg yolks, sugar, cornflour and vanilla extract in a mixing bowl, and whisk together until pale and creamy.
- Stir the milk into the egg mixture, then return to the pan and cook over a low heat, stirring constantly, until thickened. Do not allow the custard to boil. Remove from the heat and set aside to cool.
- When the custard is cold, beat in the yogurt. Pour the mixture into an ice-cream machine and churn according to the manufacturer's instructions until the mixture is thick and slushy.
- Alternatively, pour the mixture into a freezerproof container and freeze for 2 hours or until beginning to set around the edges. Tip out into a bowl and whisk well with a balloon whisk or electric mixer to break down the ice crystals, then return to the container. Freeze for a further 1½ hours.
- Meanwhile, make the purée. Put sthe blackberries in a saucepan with the sugar and 1 tbsp water. Heat until the berries are soft and juicy, then bring to the boil and boil for 1–2 minutes to reduce slightly. Remove from the heat and cool. Press the blackberries through a nylon sieve to make a smooth purée.
- If using an ice-cream machine, transfer the frozen yogurt to a rigid plastic container, then lightly stir in the blackberry purée to make a ripple effect. If frozen in a container, tip out into a bowl and whisk well until softened, then swirl in the blackberry purée and return to the container. Freeze for a further 3 hours, or overnight, until firm. (The frozen yogurt can be kept, covered, in the freezer for 3 months.)
- About 45 minutes before serving, remove the frozen yogurt from the freezer so it can soften a little. Scoop into glasses and decorate with berries.
Blackberries are not only an excellent source of vitamin C, they are also one of the richest fruit sources of vitamin E. * This delicious frozen yogurt is much lower in sugar and calories than most commercial frozen yogurts.
Some more ideas
Make blueberry ripple frozen yogurt, using fresh or frozen and thawed blueberries instead of blackberries. * Instead of vanilla extract, add 1 tsp ground cinnamon to the egg mixture in step 1. * For strawberry frozen yogurt, make the custard as in the main recipe, but omit the vanilla extract. Cool, then add the yogurt. Gently cook 500 g (1 lb 2 oz) strawberries with the juice of ½ lemon and 55 g (2 oz) caster sugar until soft. Leave to cool, then press through a sieve. Beat the strawberry purée evenly into the custard and yogurt mixture, then freeze as in the main recipe.
Each serving provides
B12 * A, calcium * B2, C, E, folate, niacin, copper, potassium, zinc