Wash and clean 800 g strawberries and puree with the powdered sugar. Set aside 400 ml puree, mix the rest with the whole milk yoghurt and 200 ml egg liqueur. Distribute the remaining egg liqueur evenly between 4 tall glasses. Pour the strawberry and yogurt mixture on top with a spoon. Carefully pour the strawberry puree over it and serve the drinks decorated with strawberries and a drinking straw.