Wash the Val Martello strawberries, remove the stalks and cut into large pieces.
Put them into a large pot, add sugar, turn well and let rest for about 12 hours. It’s important to mix now and then so that the sugar can melt.
Cook the jam by adding lemon juice and stir constantly until there is no more foam. If you like, you can mix the jam with an immersion blender or simply keep whole pieces. Pour the hot jam into preheated jars and seal immediately.