1. Put the strawberries and sugar in a bowl and mash with a fork until broken down. Add the raspberries and mash to incorporate.
2. Pour yoghurt into a bowl and beat with the icing sugar and vanilla until smooth.
3. Gently whisk in the cream (it will thicken as you whisk so don’t overdo it) and add some Chambord to taste. Ripple half the berry pulp through the cream, then spoon into pretty glasses or bowls, layering with the remaining berries.