For the yoghurt mousse, soak the gelatine in cold water for 5 minutes, squeeze it out and dissolve in 1 - 2 tablespoons of water in a small saucepan over low heat. Rinse the lemon with hot water, pat dry, finely grate the peel and squeeze out the juice.
Stir some yogurt into the liquid gelatine. Stir in the remaining yogurt and mix with lemon juice and maple syrup. Put something into the fridge. Whip the cream until stiff. When the yogurt starts to set, fold in the whipped cream. Fill the mousse into dessert bowls or glasses and place in the refrigerator for at least 2-3 hours or better overnight.
For the butterscotch sauce, halve the vanilla pod lengthways and scrape out the pulp. Heat the vanilla pod, pulp, cream, sugar, butter and sea salt in a saucepan while stirring until the sugar has dissolved. Bring to the boil and let it simmer for approx. 5 - 10 minutes without the lid, stirring, until the sauce becomes caramel-like. Let cool down.
Finely puree the mango and distribute evenly over the yoghurt mousse. Drizzle with 1 - 2 teaspoons of butterscotch sauce. Decorate with a touch of fleur de sel and serve immediately, otherwise the salt flakes will dissolve.
Tip: You can cook the sauce in advance. Sealed in jars, it can be kept in the refrigerator for 2 - 3 weeks. If you like it a little lower in calories, you can leave out the cream in the mousse.