Defrost the raspberries in a bowl for about 1 hour. Fill cookies into a freezer bag and crumble them finely with a dough roll. Melt butter in a pot. Mix cookie crumbs, oat flakes and butter.
Pour the crumb mixture into an oil-spread springform pan (24 x 24 cm) and press it down as a base. Chill for about 30 minutes.
Soak gelatine in cold water. Puree 325 g raspberries, 25 g of which should be covered and put in a cool place. Peel and puree 1 1/2 bananas. Whisk eggs and sugar with the whisk of the hand mixer until creamy.
Cream the cream cheese. Mix cream cheese, ricotta, syrup, raspberry and banana puree. Stir in egg cream. Squeeze the gelatine, dissolve and mix with 5 tablespoons of the cream cheese cream. Stir the gelatine into the remaining cream cheese cream.
Carefully fold in 250 g raspberries. Pour the mixture onto the crumb base and smooth it down. Chill for at least 3 hours.
Peel the remaining half of the banana and cut into thin slices. Remove the cake from the tin and cut into pieces. Decorate with raspberry puree and banana slices.