Instructions

1. Put a small plate into the fridge.
2. Wash and pit the cherries, then put them in a heavy-based pan.
3. Add the sugar, cinnamon stick and vanilla. Squeeze the mandarin juice over the cherries, then cut it into 4 pieces and add to the pan.
4. Bring to the boil and cook until the sauce thickens but it's still runny. Remove the cinnamon stick and mandarin pieces. Lightly crush the cherries with a potato masher and simmer until the sauce has thickened and started sticking to the pan. Turn down the heat.
5. Add a few drops of jam onto the chilled plate. Put it in the fridge for a minute, then run your finger through the jam - if it forms a crinkle and is tacky, it's ready. If it’s not quite ready, cook for another couple of minutes at a time and re-test.
6. Once the jam is ready, ladle it into hot, sterilized jars and place the lids on immediately.
7. Allow the jars to cool, then store them in a cool, dark place. Once opened, store the jam in the fridge.