Vanilla Mascarpone Cream Hearts with Raspberries and Blackberries

This is one of the serious classics of French cooking and uses a soft white cheese as its base. My version combines mascarpone and yoghurt to give a more complex, sharp and interesting flavour that works in heady harmony with red summer berries. The cream is formed in traditional heart-shaped porcelain moulds that have holes in the base to allow whey to drain away, giving the cream a firmer texture. After the cream has been refrigerated for several hours, it is unmoulded to reveal its perfe