It is best to have the meat in one solid piece, but if it is boned and rolled, make sure it has no added covering of suet. Combine the vinegar, wine, water and seasonings, pour this mixture over the meat. Add the sliced onions. Keep meat in the refrigerator, covered with marinade, for 1-3 days, turning occasionally. (Purists say it should be 3 days; I find 1 day sufficient.) Remove meat from marinade, wipe dry with paper towels and brown in the shortening over high heat, sprinkling with 1 tablespoon flour. Strain and add marinade, cover, lower heat and cook gently for 4-5 hours, until fork-tender. Remove meat and keep in warm place. Pour off the stock. In the same kettle, melt the butter, add the remaining flour and the sugar, stirring until smooth and browned. Slowly add the stock, cooking until smooth and thickened. Add the crushed gingersnaps, and cook until dissolved. Replace meat in the sauce and cook 1/2 hour longer. Meanwhile, cook noodles to serve with the sauerbraten. This dish tastes better the second day.