Stone the plums. Place them in a large saucepan and sprinkle with sugar. Cover the pan, place it over low heat, and leave the plums to stew for 3 to 4 minutes. Leaving the pan covered, turn off the heat and let the plums stand for 10 to 12 minutes to continue to soften. Transfer the plums to a sieve set over a bowl to allow their juices to drain away. Now tip the plums into a bowl and leave them to cool completely.

Meanwhile, mix the orange juice and zest with the yogurt. Lightly crush the plums with a fork to make them more of a puree, then gently swirl them into the yogurt to create an attractive marbeled effect. Spoon the dessert into two glasses, and serve with some ginger cookies.