Roast the oat flakes in a pan without fat and let them cool down. Mix yoghurt, sugar and vanillin sugar. Pour the sour cream into a mixing cup and whisk with the whisk of the hand mixer until creamy.
Fold the sour cream under the yoghurt mass. Divide the raspberries into 4 glass bowls and pour the cream over them. Stir a teaspoon of jam into the cream and sprinkle with oat flakes. Decorate with raspberries and lemon balm as desired.