Preheat oven to 325 degrees F.
Heat a Dutch oven over high heat until hot. Add oil and butter. Season the roast with salt and pepper. Dredge roast in flour.
Brown the roast evenly on all sides, about 10 minutes. Transfer to a platter and set aside.
Reduce the heat to medium. Add onions, carrots, celery and leeks to the Dutch oven and sauté until soft and golden, about 5 minutes. Add garlic and cook another 1 to 2 minutes or until garlic is soft. Add cinnamon stick, ginger, nutmeg, black peppercorns, cloves,
Rosemary, thyme, savoury, bay leaves. Stir in tomato paste, grainy mustard. Add wine, stock and tomatoes. Let liquid come to a boil and reduce slightly (by about a quarter), about 5 to 10 minutes.
Place the meat back into Dutch oven. Cover with lid. Transfer to oven and braise, about 4 hours, basting and turning meat as it cooks, adding the potatoes midway during the cooking process depending on size of the potatoes. Cook meat until fork tender, another 1 hour. Transfer meat to a platter. Tent with foil and let rest. Garnish with chopped chives. Check seasoning, add more salt and pepper if needed. Add meat back in the pot. Serve.