900 grams blackberries
50 ml cold water
50 ml fresh lemon juice
500 grams granulated sugar
Put the fruit into a large heavy-based saucepan, add the water and the lemon juice, and bring to a boil. Once it comes to a rolling boil, lower the heat and simmer for 20-25 minutes until the fruit softens. Tip in the sugar, turn the heat down to low, and stir until the it completely dissolves. When dissolved, bring the heat up to medium, bring to a rolling boil, and then boil for about 20 minutes, skimming off the foam as you go.
Test the jam for setting point by placing a little bit of jam onto a chilled plate. After a minute, gently push your finger through the jam and if the surface wrinkles, it’s ready; if it doesn’t, keep cooking for 2-minute intervals, testing in between. If you use a sugar thermometer to test for doneness, it should read 105˚C. Remove the jam from the heat, skim off any excess foam, let it cool down for about 15 minutes, then pour into sterilised jars and seal.
