For the marinade and beef:
2 cups water
1 cup dry red wine
1 cup red wine vinegar
2 medium carrots, peeled and chopped
2 medium celery stalks, chopped
1 medium onion, halved and sliced
2 cloves garlic, smashed
1 tablespoon whole black peppercorns
1 tablespoon juniper berries
1 tablespoon mustard seeds
2 bay leaves
1 (3- to-4 pound) beef chuck roast or bottom round roast
For cooking and finishing the roast:
1 1/2 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1 tablespoon olive oil
2 tablespoons unsalted butter
2 tablespoons all-purpose flour
Marinate the beef: Stir all the ingredients except the beef together in a large saucepan. Bring to a boil over medium-high heat, then remove from the heat and cool completely.
Place the beef in the bowl of a 6-quart or larger slow cooker and pour in the cooled marinade. (The meat will not be completely submerged.) Cover and place the bowl in the refrigerator to marinate for 2 days, flipping the meat once or twice per day.
Slow-cook the beef: Remove the beef from refrigerator about 30 minutes before cooking. Transfer the meat to a large plate and pat completely dry with paper towels. Do not discard the marinade. Generously season the meat all over with the salt and pepper.
Heat the oil over high heat in a large cast iron or heavy-bottomed skillet until shimmering. Add the beef and sear each side until deeply browned, 4 to 5 minutes per side.
Return the beef to the marinade in the slow cooker. Cover with the lid. Cook until the beef is tender and cooked through, 8 to 9 hours on LOW, or 5 to 6 hours on HIGH. Transfer the beef to a cutting board and rest for about 5 minutes.
Meanwhile, strain the cooking liquid through a strainer or colander set over a bowl. Measure out 2 cups of the liquid and set aside (discard the remaining cooking liquid and solids).
Melt the butter in a medium saucepan over medium heat. Whisk in the flour and cook, whisking constantly, for 1 to 2 minutes. Gradually whisk in the 2 cups reserved cooking liquid. Cook, whisking frequently, until thickened, 3 to 4 minutes. Slice the meat and serve hot.
Recipe Notes
- Storage: Leftovers can be stored in an airtight container in the refrigerator for up to 3 days.