Wash and stone the plums. If they are small, leave them halved but if they are large, cut into quarters.
Put them in a wide, shallow pan with the sugar, one half of the vanilla pod, strips of lemon peel and 1 tablespoon water. Then bring slowly to the boil, stirring occasionally until the sugar has dissolved.
Now reduce the heat to a gentle simmer and continue cooking until the plums are soft but still keeping their shape, about 10–15 minutes. Set aside to cool.
Meanwhile, put the cream in a small pan with the remaining half of vanilla pod. Heat until it just begins to simmer and then pour into a bowl and leave to cool. Cover and chill until needed.
Next put the almonds in a small frying pan/skillet and, over a gentle heat, toast until they are just beginning to turn colour and smell nutty. Toss them frequently. Leave to cool and then chop.
Once the plums are cool, discard the vanilla pod and lemon strips. Test for sweetness. Adding 2 teaspoons of caster/superfine sugar if they are still a little tart.
Spoon the plums and their juice into the four glass dishes.
Now remove the vanilla pod from the chilled cream and add the yogurt. Whisk gently until the mixture has softly thickened and holds its shape.
Spoon the cream mixture over the plums and level the surface.
Sprinkle 1 rounded teaspoon of the muscovado/soft dark brown sugar over the cream in each pot.
Finally sprinkle over the chopped almonds.
Cover and chill for 3 hours. (The sugar on the top will melt.)