Peel and core the pears. Mix together with mascarpone, yoghurt, sour cream, cane sugar and lemon juice to a creamy mass.
Line a glass baking dish with ladyfingers and drizzle 4 cl blueberry liqueur over it. Now layer alternately as follows: Spread a thin layer of cream (so the blueberries cannot roll away), spread 250 g of blueberries, cream, ladyfingers - again drizzled with blueberry liqueur, thin layer of cream, blueberries and finally another layer of cream.
Place in the refrigerator for at least 4 hours (preferably overnight) until eaten. Serve sprinkled with cocoa powder.