Place the blueberries in a lidded tupperware box and mash until broken down.
Add the chia, xylitol and half of the water to the container.
Stir until all combined.
Leave to stand for a few mins and add more water.
The chia will soak a considerable amount of liquid so do not worry if it looks quite watery at this stage.
Add the lid to the box and secure. Place in the fridge overnight and the jam will be ready to eat by the morning.
Store in the fridge for up to 5 days.