100 g (3.5 oz / 1 cup) blackberries
80 g (2.8 oz / ⅓ cup) white granulated sugar
240 ml (8.1 oz / 1 cup) water
20 g (0.71 oz / ⅙ cup) cornstarch
Put the fruit in a saucepan.
Add sugar, cornstarch, and water, and mash to a pulp.
Simmer or boil, uncovered, to reduce moisture.
Serve hot over ice cream, or cold as jam.