1. Place the wine, vinegar, water, onions, celery leaves, salt, sugar, mustard seeds, nutmeg, cloves, peppercorns, parsley, and bay leaves in a large mixing bowl and mix well.
2. Add the meat, cover and leave to marinate for 2-3 days (or at least 24 hours) in a cool place, turning several times.
3. Remove the meat from the marinade (reserving the marinade) pat dry on kitchen paper and season with salt and pepper.
4. Heat the lard or oil in a large saucepan, add the meat and brown on all sides.
5. Add the reserved marinade, bring to the boil then reduce the heat, cover and simmer gently for at least 3 hours.
6. Strain the cooking liquor into a measuring jug then pour about 120ml/4fl.oz. of the liquor into a saucepan. B bring to the boil, then add in the crushed gingernuts and the remaining liquid, a little at a time, stirring constantly.
7. Continue to boil the sauce, stirring, until thickened. Adjust the seasoning.
8. To serve - slice the meat and transfer to a warmed serving platter. Pour a little of the sauce over the top and serve the remaining sauce separately in a gravy boat.