Put the carrots, onion, garlic, thyme, bay leaf, and cloves or allspice in the bottom of a slow cooker crock. In a measuring cup or bowl, whisk together the broth, wine, and tomato paste to blend.

Set a large heavy-based skillet over medium high heat. Pat the roast dry with paper towels, rub both sides with the olive oil, and sprinkle generously with salt and pepper. Sear the roast in the skillet until a dark crust forms on one side, 3 to 5 minutes. Turn and sear the other side, 3 to 5 minutes. Reduce the heat to medium and put the roast on top of the vegetables in the crock. Add the broth mixture to the skillet, bring to a simmer, and scrape the pan bottom to loosen any browned bits. Pour the liquid over the roast and cover the crock; don't stir. Turn the slow cooker to low heat; cook gently without lifting the lid until the roast is fall-apart tender, 8 to 10 hours.

Transfer the roast to a cutting board and tent with foil to keep warm. Strain the contents of the crock through a sieve set over a medium saucepan. Discard the solids. Skim the fat from the top of the strained liquid (or use a fat separator). Bring to a boil and then simmer rapidly until reduced by half, about 10 minutes. Whisk in the brandy, horseradish, and mustard. In a small bowl, mix the flour into the sour cream, stir in a few tablespoons of the sauce, and then pour the sour cream mixture into the sauce, whisking vigorously to blend. Cook over medium heat, stirring occasionally, for 5 minutes to blend the flavors. Meanwhile, slice the roast thinly. Serve with the gravy and a sprinkling of parsley.

Pot roast without a slow cooker:

If you don't have a slow cooker, you can still make this pot roast, just make the following modifications to the recipe. Heat the oven to 250° F. Sear the meat in a heavy Dutch oven or similar pot. Transfer the meat to a plate. Add the broth mixture to the pot and bring to a simmer. Return the meat to the pot and turn once to coat the meat in the broth. Scatter the vegetables and herbs around the meat, return to a simmer, cover tightly, and roast in the oven until the meat is very tender, about 4 hours. Check occasionally to be sure the broth isn't bubbling too rapidly, and flip the meat if the top surface looks dry.