Combine the vinegar, water, onion, bay leaves, peppercorns, and a pinch of salt in a saucepan. Simmer for 5 minutes, cool completely, and pour over the beef.
Cover and refrigerate for 2 to 3 days, turning the roast once or twice.
Braise the Roast:
Remove the beef from the marinade and pat dry. Strain and reserve the marinade. Brown the beef in butter in a Dutch oven.
Pour in the marinade, cover, and braise at 325 F until fork-tender, about 3 hours, turning once.
Make the Gravy and Serve:
Transfer the beef to a board. Whisk the flour and ginger snaps into the braising liquid and simmer until thickened, about 8 minutes.
Slice the beef and serve with gravy, red cabbage, potato dumplings, and parsley.
Notes
Cool the marinade completely before adding the beef.