Poke holes in the meat with a skewer or needle and then marinate in buttermilk (use a bowl or ziplock bag). Allow it to marinate in the refrigerator for several days (at least 2 days).
Remove the buttermilk and dry off meat with paper towels. Salt the meat with Kosher salt and add fresh ground pepper. In a heavy, flameproof casserole, brown on all side in butter and olive oil. Remove meat from casserole and pour out the browning fat.
Add the onion and saute. Add wine, beef stock, thyme and peppercorns, bring to a boil and skim. Return pot roast to casserole and bake at 300 degree, covered, for several hours or until tender. One hour before serving add potatoes and carrots. At this point, you may want to add more water if necessary.
Remove meat and vegetables to a platter and bring the remaining sauce to a boil on the stove. Spoonful by spoon ful, add arrowroot mixture until desired thickeness is obtained. Season to taste.
Original recipe from Nourishing Traditions by Sally Fallon