Ingredients: washed blackberries (weigh them), the same amount in sugar and a lemon.
Mix the berries with the sugar, squeeze the juice of the lemon and grate the rind and put everything on a pan.
Set the gas to low and stir continuously until the mixture bubbles with some effort - when it starts spitting bits around is time to stop, it might take from half an hour to 45 min. Then you pour it immediately into jars.
You might need some help as the stirring is a bit tiresome!
Helpers can also make labels, yes, those are blackberries!
Sterilise some jars using boiling water or a steam steriliser. Once the jam is done pour it into the jars while boiling hot and close the lids tight.
tenfoot jam, yum!