1. First sterilize the glass jars* and lids – either by boiling them in plenty of water or heating them in the oven. Be careful with the lids, they might not withstand the same heat as the glass jars. Set aside and let dry.

2. Wash the blackberries and let them drain properly.

3. Mix the xylitol, gelling powder (Gelierfix), and vanilla powder in a tall saucepan. Add the blackberries and lemon juice, then purée everything using an immersion blender*. If you want some larger pieces, purée only briefly.

4. Bring the mixture to a boil, then let it boil vigorously for about 4–5 minutes while stirring constantly. Do a gelling test (using a small plate) – if the jam sets quickly, it is ready to be canned. If not, simply cook it a little longer.

5. Pour the jam into the prepared glass jars and seal them tightly immediately. There is no need to turn the jars upside down. Let them cool completely. Store the jars in a cool, dark place (e.g. basement). If you worked with clean equipment, the unopened jam should keep for 1–2 years. Once opened, store in the fridge and consume within 2–6 weeks.