Put the cleaned fruits in a large saucepan. Mix the Gelfix with the agave syrup well with the whisk. Add this mixture to the fruit in the saucepan and stir well. Bring to the boil and simmer for a good 3 minutes.
In the meantime, chop the walnuts and add them to the saucepan with the vanilla essence. Let it boil again.
Rinse the prepared glasses with cold water and pour in the jam. Screw on tightly and let it cool upside down. Makes about 4-6 glasses.