Raspberries and blueberries selected. Wash and drain the blueberries and strawberries. Wash and quarter the strawberries. Mix the berries and 3 tbsp. sugar and place in a large flat casserole dish.
Separate eggs. Whip the egg whites and 100 g cream separately in two high mixing bowls until stiff. Whip egg yolk, cinnamon and 75 g sugar for 5-6 minutes until light creamy. First fold the beaten egg whites and then the cream into the egg yolk mixture.
Spread on the berries. Bake in the preheated oven (electric oven: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 25 minutes until golden brown.
Dust the berry gratin with icing sugar. Whip 100 g cream until semi-stiff and add.