(makes 3-5 jars) Prepare a juice bag, sterilize and hang.
Place apple pieces, blackberries, juice of one lemon, and water in a large heavy saucepan. Bring to a boil, then simmer for 20-25 min or until fruit is completely soft. Fruit mixture into juice bag form and drain for 8 hours or until all juice has run through.
Rinse jam jars thoroughly with hot water. To dry and warm them, put them in the cold stove and heat it up to 130 °C. Dry for 10-15 min.
Measure the juice. To 600 ml of juice add 450 g of sugar. Put both together in the cleaned saucepan, heat on low temperature until the sugar is completely dissolved. Add crem de cassis to taste. Let it bubble and make 10-15 min or until the quantity gels.
Skim well. Fill jelly to rim in prepared jars, close tightly. Keep cool and dark.