Rinse the roast, pat dry and sprinkle generously all over with pepper. Melt the butter in a 10 to 12-inch nonstick frying pan over high heat. When hot, add the roast and brown it well on all sides, 6 to 8 minutes total.
Meanwhile, cut the carrots into sticks about 3/8? thick and 2-inches long. In a 4.5 quart or larger slow cooker, combine the carrots, onion, celery, garlic, thyme, peppercorns, and bay leaf. Set the roast on top of the vegetables; add the drippings. In a small bowl, stir together the wine and the tomato paste; pour over the meat and vegetables.
Cover and cook until the roast is very tender when pierced, 8 to 9 hours on low, or 5 to 6 hours on high. If possible, turn the meat over halfway through cooking.
With 2 slotted spoons, transfer the meat to a platter; keep warm. Skim and discard any fat from the cooking liquid. Turn the slow cooker to high. In a small bowl, blend the cornstarch with 1 ½ tablespoons of water; pour into the slow cooker and stir often until the sauce is bubbling, 10 to 15 minutes.
PREPARE THE POTATOES:
Scrub and peel the potatoes; cut into 1½-inch chunks. Bring the potatoes to boil in a large pot of water; reduce the heat, cover and simmer until the potatoes mash easily when pressed, 20 to 25 minutes. When the potatoes are done, heat the cream and butter in a microwave-safe container just until steaming (don’t boil), 1 to 3 minutes. While the cream is heating, drain the potatoes and mash in the pan with a mixer or potato masher until almost smooth. Add the cream, a portion at a time, and mix until the potatoes have the consistency desired. Stir in salt, pepper and desired amount of horseradish to taste.
With a slotted spoon, lift the vegetables from the slow cooker and arrange them on a platter beside the meat. Spoon the horseradish smashed potatoes onto the platter; sprinkle with parsley. Spoon the sauce over meat.
Slice the meat and serve with the vegetables, potatoes and sauce, adding salt to taste- as desired.
Notes
*If watching calories, substitute fat-free chicken broth for the cream in the smashed potatoes.