Steps
- Wipe and hull 1kg of strawberries, halving large berries. Toss with 750g of jam sugar with added pectin and leave uncovered for 12 hours.
- Transfer to a wide nonreactive preserving pan with the juice of 1 lemon. Heat gently, stirring until the sugar dissolves; brush down any crystals with water.
- Boil hard for 5-10 minutes, until a thermometer reads 221°F / 105°C. Remove from the heat and skim off the foam.
- Let settle for 15 minutes, then ladle into warm sterilized jars. Cover, cool, and refrigerate.