Pick the berries, rinse and add to a pot with lemon juice and 250 ml (approximately 1¼ cups) of water. Bring to a boil. Simmer for about 5 minutes over low heat. Line a sieve with a cloth and place over a bowl. Let the berries drain in it overnight.
The next day, pull the cloth from the sieve and squeeze out the berry juice. Mix the berry juice (if necessary fill up with water to 1 liter, approximately 5 cups) with the jam sugar and the crème de cassis in a pot, bring to a boil, cook for about 4 minutes until bubbly (setting point). Fill in prepared jars and seal tightly. Invert the jar and let stand for 10 minutes, turn around and leave to cool. Store in a cool and dark area.
Tip: To preserve the jam for longer, you will need to process the jars according to manufacturer's instructions, or visit