Place Eisbeins with beer, fruit juice, herbs, peppercorns and onion in a heavy based pot and cover with a tight fitting lid
Bring to the boil and reduce heat. Simmer at low heat for 1 hour or until the meat is very tender
Top up the cooking liquid with hot water at frequent intervals if necessary. Do not let the liquid level in the pot reduce to a very small amount. Turn Eisbeins over now and then
When tender, remove Eisbeins and keep hot on a serving plate
Strain liquid to remove herbs and onion, pour liquid back into pot and increase heat
Reduce liquid to approx 250 – 300ml. Thicken liquid with a cornflour and water paste and beat until smooth
Add mustard and sugar and stir through. Pour sauce and serve hot.