Wash, clean and halve the strawberries thoroughly. Mix jam sugar, strawberries and lemon juice in a high saucepan. Bring to the boil while stirring constantly and let it boil effervescently for exactly 3 minutes from the beginning of foaming. Mash some of the fruit with a potato masher. Pull the pot off the stove.
Stir in liqueur. Fill jam full to the brim into prepared twist-off jars and close. Leave to stand on the lid for about 15 minutes. Store as cool and dark as possible
Shelf life approx. 6 months