Mix together the yogurt, crème fraîche, powdered sugar and lemon zest. Then beat the egg white until stiff and fold in. Place the mass in a wire sieve lined with cheesecloth and allow to drain for 8 to 20 hours. Then fall.
Puree the raspberries with the powdered sugar and pass through a sieve.
The sauce e.g., serve as a sauce, cut out the yoghurt foam with a spoon and serve with the fruit and mint.