Peel the ginger and cut into large pieces. Bring 300 ml water, currant juice, apple juice, Glühfix, star anise and ginger to the boil and leave to stand for 5 minutes. Pour everything through a fine sieve and let it cool down.
Wash the kumquats, rub dry and cut into 1/2 cm wide slices. Bring the liquid, jam sugar and kumquats to the boil and simmer for 3-5 minutes. Pour into glasses, close them tightly and let them get firm.