- 800 g Strawberries
- 2 tsp Citric acid ((or substitute juice of a lemon))
- 1 kg sugar
- a knob of butter
- Rinse out a preserving pan, or very large saucepan, but do not dry.
- Hull the strawberries and roughly chop, then add to the preserving pan and sprinkle with the citric acid (or lemon juice).
- Cover the preserving pan with foil or heatproof clingfilm, then set on a low heat for 20 minutes, shaking the pan occasionally.
- Wash and dry 4 jam jars, and set onto a baking sheet, jars and lids separated and upright. If available, place a jam funnel and metal ladle on the baking sheet too.
- Transfer the baking sheet into a cold oven, and set the temperature to 140c (285f).
- Place a couple of saucers into the freezer, ready to test for set later.
- After 20 minutes, use a potato masher to turn the cooked strawberries into a chunky puree.
- Add the jam sugar, and turn up the heat to medium/high. Stir the jam mixture periodically as it heats.
- Bring the jam to a rolling boil. If you have a probe thermometer, bring the jam to at least 105c (220f) before you test for set.
- To test for set, remove jam from the heat, and allow the surface to settle. Spoon a dollop of the hot jam onto one of the cold saucers and set a timer for 5 minutes.
- While you are waiting, stir a knob of butter into the hot jam, and then use a metal spoon to skim off the scum.
- After 5 minutes, you can test for set; Push your finger through the blob of jam, and check if the surface wrinkles up over your finger. If it does, your jam will be sufficiently set.
- If not set, or if a firmer set is preferred, return to the boil for another few minutes and test again.
- Leave the jam to cool for 20-30 minutes.
- Remove the baking tray from the oven and equip heatproof gloves.
- Ladle the jam into the hot jars, and use a magnet to lift the lids into place. Screw on tightly and leave to cool completely.
- Stored in a cool dark place, the jam will keep well for over a year.