Chop the strawberries and place them in a saucepan together with the water.
Bring to the boil (lid on), then turn down the heat medium and let it bubble away for 15 minutes. Only add the lemon juice if you want to store the jam for longer than 1 week - it prevents the growth of bacteria.
Mash the strawberries with a potato masher (or with a fork), then continue to cook on low-medium for another 30 minutes until reduced by half. You want it to bubble peacefully. Bubbles will become smaller as the liquid evaporates. Stir regularly with a spatula to prevent the jam from burning. Towards the end of cooking, stir constantly.
Taste. If necessary, sweeten with 1 tbsp of powdered erythritol.
Add the ground chia seeds and stir. Cool and fill into a sterilised jar. Store in the fridge.
The amount of sweetener needed depends on the ripeness your strawberries. I made this recipe when strawberries were out of season, that's why I decided to add 1 tbsp of sweetener. If yours are sweet from the get-go, you may be able to omit the sweetener altogether.I prefer to use ground chia seeds for this jam so I don't get any gloopy chia seeds in it. I simply ground a whole bunch of chia seeds in my food processor until they resembled a powder. They're great for thickening anything in low carb cooking, including sauces. The exact cooking time will depend on the saucepan you use and how hot your stove is. Simply cook until the jam is thick. The thicker it is, the more natural sweetness it will have. My 400g (14.2oz) of strawberries made 200g (6.7oz / scant cup) of jam. I calculated 1 tbsp = 14g as one portion/serving.