Wash and de-hull the strawberries, and pat dry.
Sprinkle in the sugar, and mix gently so as not to crush the strawberries. Leave as-is for half a day (or overnight).
This photo shows how it looks after leaving it overnight. Separate the berries from the juice.
Pour the strawberry juice from Step 3 into an enamelled pan, and simmer and reduce over medium heat.
After simmering for 5 minutes, when the juice has thickened, add the berries from Step 3 and half the lemon juice. Keep cooking for 8 to 10 minutes, while it's still a bit liquid.
Add the remaining lemon juice, simmer for another minute or so and turn off the heat.
Done Fill a jar sterilized in boiling water up to the rim. Screw on the lid and let the jar cool upside down - you will be able to keep the jar at room temperature this way.
Story Behind this Recipe
I make strawberry jam every year in the spring, but it's a shame that the berries disintegrate if you cook them for a long time. So I figured out a way of retaining the shape of the berries by staggering the cooking times for the berries and juice.
Small berries are better suited for this recipe. The jam will thicken when it's cool due to the pectin, so stop cooking when it's still a little liquid.