According to my grandmother’s recipe
3 kg of ripe strawberries
1 ½ kg of sugar
Rinse and cut the stems of the strawberries. Pop them in a saucepan, add the sugar and bring to a boil. Do not add water, strawberries give off a lot of juice. Stir often with a wooden spoon.
Simmer at small bubbles until the sauce thickens leaving a mark on the bottom of the dish when stirred.
Divide the jam into clean, warm jars. While the jam is still boiling, close the jars and turn upside down to vacuum seal them.
Store the strawberry jam in a dry, dark and ventilated place.