Heat the berries gently in a pan with the golden caster sugar for about 5 minutes, just until the sugar has dissolved and the fruits have thawed.
Drain the berries through a sieve and return the juice to the pan and warm it through. Mix the arrowroot with 1 tablespoon cold water to make a smooth paste. Add to the warm juices in the pan and stir together until thickened and smooth.
Arrange the ratafias in the base of a large glass compôte or individual compôtes. Pour over the red vermouth. Spoon over the fruits and thickened juice.
Whip the cream lightly and reserve half in the fridge. Melt the white chocolate in a bowl over a pan of simmering water (see
Mix together the yogurt, light muscovado sugar and chilled whipped cream from the fridge. Spoon over the top of the custard, smooth over the surface and sprinkle with the extra crumbled ratafia biscuits.