Sterilize your jars and lids by washing them in hot, soapy water and either boiling them for 10 minutes or placing them in a 120°C (250°F) oven for 15 minutes; keep jars hot until ready to fill.
Hull and halve or roughly crush the Strawberries so they release their juice — you can leave some pieces chunky for texture or mash more finely for a smoother jam.
Place the prepared strawberries in a large, heavy-bottomed saucepan or bowl and add Granulated Sugar. A common ratio is equal weight sugar to fruit (1:1) for a classic set, or use ¾ to 1 by weight depending on how sweet/tart you prefer; mix well.
Let the fruit and sugar macerate at room temperature for 1–3 hours (or refrigerate overnight) until the sugar has dissolved and the fruit has released plenty of juice.
Transfer the macerated fruit and any collected juices to a heavy saucepan and bring gently to a boil over medium heat, stirring often to prevent sticking. Once boiling, reduce to a steady simmer.
Skim off any foam that forms on the surface and continue to simmer, stirring frequently and gently pressing larger fruit pieces with a spoon, until the mixture thickens — this can take 10–30 minutes depending on volume and desired texture.
About 5 minutes before you expect the jam to be done, dissolve a small pinch (roughly 1/4 teaspoon per kilogram of fruit) of Citric Acid in a tablespoon of water and stir it in to brighten the flavor and help the jam set. Test readiness by spooning a small amount onto a chilled plate — if it wrinkles when pushed, it’s done.
Remove the pan from heat. Using a ladle, pour the hot jam into the prepared hot jars, leaving about 1/4 inch (6 mm) headspace. Wipe rims clean, seal with lids, and let jars cool upright until the lids seal (you should hear a pop).
For longer shelf life, process filled jars in a boiling water bath for 10 minutes (adjust time for altitude). Store sealed jars in a cool, dark place for up to a year; refrigerate after opening and use within a few weeks.
