Ingredients needed:
Blackberries
Sugar
Pectin
Lemon Juice
Place the fresh berries and sugar in a bowl for a few hours (or overnight). During this time, the berries will macerate, and the sugar begins to dissolve – thus needing less time to cook before the sugar fully dissolves, allowing the berries to stay more in-tact.
Start by very lightly mashing the blackberries in a bowl (or the pan) using a potato masher or similar tool.
Then, in a medium heavy-based pan, add the sugar, blackberries, lemon juice, and pectin. Heat on low-medium heat, stirring constantly, to completely dissolve the sugar. This will eliminate the risk of grainy/sugar crystal-formed jam later on.
Bring the mixture to a boil (a rolling boil that can’t be stirred down) at high heat for five minutes, without stirring. Use a spoon to make sure the jam isn’t sticking to the bottom of the pan. If it is, then you can mix it a couple of times and reduce the heat slightly.
To check that the jam has reached the setting point, either use a thermometer or the saucer test. If using a thermometer, the temperature needs to be 105ºC/220ºF.
For the saucer test, it’s best to have placed a saucer in the fridge/freezer before starting the jam. After five minutes, add a spoonful to the sauce and wait 30 seconds. Push it with your finger, and if it wrinkles, even a little, then it will set.
Skim off any of the excess foam on top of the pan, for a clean jam. You can also add in a small amount of butter right at the end and stir to help disperse the rest of the foam/scum.
Remove from heat and leave the jam to cool for 10-15 minutes. This will allow the berries to settle so that they don’t sink to the bottom in the jars.
Meanwhile, sterilize the jars you will be using for the jam and then place them in the oven for 10 minutes at 160ºC/325ºF to completely dry.
Place the jars onto a wooden surface and transfer the jam to the jars. This process is easier with a canning funnel, but not necessary.
Wipe away any spillage on the outside of the jar with a damp cloth and then seal the jars. Be careful not to touch the lip or inside the lid if you’re hoping to properly ‘can’ your jam.”
(Recipe example and image from https://www.alphafoodie.com/easy-homemade-blackberry-jam-recipe/)