Jam with blueberries.

Growing and making jam with blueberries | Life and style | guardian.co.uk:
Makes 1.25kg
600g rhubarb
300g blueberries
2 limes, the zest and juice
700g sugar

Wash rhubarb, top and tail then chop into evenly sized pieces (I usually run a knife down the middle of the stalks then chop into roughly 1cm sized pieces). Place in a glass bowl and pour the sugar over the top. Cover with a plate or cling film and leave overnight, by which time the sugar will have soaked up the juice from the rhubarb.

Place the grated lime zest and blueberries in a pan, adding 3 tblsp of lime juice. Heat gently and simmer for 15 minutes with the lid on, until the berries are cooked and surrounded by juice.

Pour the rhubarb and sugar into a jam pan and stir over a low heat until the sugar is completely dissolved. Add the blueberries and lime, turn up the heat and cook at a rolling boil until setting point is reached (a small dollop of the syrup on a cold plate will readily form a skin when left to cool slightly). It took me 10 minutes to achieve this and I advise that you keep an eye on it and give the occasional stir whilst it cooks as the mixture is apt to burn if you're not careful.

Skim if necessary. Pour into hot sterilised jars, put a circle of waxed paper on the surface of each one and seal.

This jam has a nice soft set that suits me fine. If you prefer your jam to 'cut' rather than dollop substitute all or half of the sugar with preserving sugar that includes added pectin.
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