INSTRUCTIONS
1. MARINATE BEEF Combine water, vinegar, onions, carrot, celery, peppercorns, and bay leaf in large non-aluminum pot. Submerge beef, cover, and refrigerate 4 hours or up to 24.
2. BROWN BEEF Adjust oven rack to middle position and heat oven to 225 degrees. Remove beef from marinade, pat dry with paper towels, and season with salt and pepper. Strain marinade through fine-mesh strainer; reserve vegetables, bay leaf, and peppercorns and discard liquid. Heat 1 tablespoon oil in Dutch oven over medium-high heat until just smoking. Brown roast on all sides, 8 to 12 minutes. Transfer to plate.
3. COOK VEGETABLES Add remaining oil and reserved vegetables to empty Dutch oven and cook until lightly browned, about 5 minutes. Stir in allspice and ginger and cook until fragrant, about 1 minute. Add broth, wine, and prunes and bring to simmer.
4. BRAISE BEEF Return beef, along with any accumulated juices, to pot, cover, and transfer to oven. Bake, turning beef halfway through cooking, until completely tender, 5 to 6 hours. Transfer beef to carving board, tent with foil, and let rest 30 minutes.
5. MAKE SAUCE Remove 1 cup braising liquid; reserve. Bring remaining liquid to boil over medium-high heat. Add gingersnaps and cook, whisking occasionally, until sauce is thickened and reduced to 6 cups, 10 to 15 minutes. Off heat, whisk in butter. Strain sauce through fine-mesh strainer into serving bowl; discard vegetables and spices. Season with salt and pepper.
6. SLICE ROAST Slice beef thinly across grain and transfer to rimmed baking dish. Pour reserved braising liquid over meat. Serve with sauce.
