Let the strawberries thaw or wash the fresh strawberries and remove the green deposits.
Put the strawberries, bananas, lemon juice and the scraped pulp of the vanilla pods in a large saucepan and puree with the hand blender. Add the preserving sugar and stir in. Bring to the boil while stirring, let it simmer for four minutes and keep stirring.
Pour into glasses, turn upside down for 5 - 10 minutes and then leave to cool.
Depending on the size, it makes about 5 - 6 glasses.