Wash, clean and chop the strawberries. Mix with the preserving sugar and lemon juice. Cut the marshmallows into small pieces, stir in the cream, bring to the boil and simmer over low heat until the marshmallows have melted. Cut the vanilla pod lengthways, scrape out the pulp. Add the vanilla pulp and pod to the strawberries, bring to the boil and cook for about 4 minutes, stirring constantly. Take off the stove, remove the vanilla pod,
Use a jam funnel to fill the jam 2/3 high into the sterilized twist-off jars. Pour the very hot marshmallow cream on top and stir with a spoon handle. Close the jars and put them on the lid for about 5 minutes, turn them over again and let them cool down.