Preheat oven to 375 degrees.
Rinse and dry shanks and season liberally with salt and pepper. In a heavy-bottomed Dutch oven with a lid, heat olive oil until smoking. Sear shanks until dark golden brown over medium heat, about 15 to 18 minutes. Remove shanks and set aside. Add onion, garlic, rosemary and artichokes and cook until softened, about 8 to 10 minutes. Add olives, wine, tomato sauce and chicken stock and bring to a boil. Replace lamb shanks in pan and return to boil. Cover tightly and place in oven and cook for 1-1/2 hours, until fork tender. Remove and serve with soft polenta.
Saute the onion and garlic in the olive oil over medium heat until translucent, but not brown (about 10 minutes). Add the thyme and carrot and cook 5 minutes more. Add the tomatoes. Bring to a boil, lower the heat to just bubbling, stirring occasionally for 30 minutes. Season with salt to taste. Serve immediately, or set aside for further use. The sauce may be refrigerated for up to one week or frozen for up to 6 months.