To prepare osso buco, heat a large Dutch oven over medium-high heat. Coat pan with cooking spray. Add the onion, carrot, and 6 garlic cloves; sauté 7 minutes or until tender. Remove onion mixture from pan.
Place flour in a shallow dish. Sprinkle lamb with 1/2 teaspoon salt and 1/4 teaspoon pepper; dredge lamb in flour. Melt 1 teaspoon butter in pan over medium-high heat. Add 3 lamb chops; cook 3 minutes on each side or until browned. Remove lamb from pan. Repeat procedure twice with remaining butter and lamb.
Return onion mixture to pan. Add wine; cook 4 minutes or until most of liquid evaporates. Add 3/4 teaspoon salt, 1/4 teaspoon pepper, thyme, tomatoes, and broth. Return lamb to pan; bring to a boil. Cover, reduce heat, and simmer 1 hour. Uncover and simmer 45 minutes or until lamb is tender. Remove lamb from pan; cover and keep warm. Discard thyme sprigs.
Strain cooking liquid through a sieve into a large bowl, reserving vegetable mixture. Place a heavy-duty zip-top plastic bag inside a 2-cup glass measure. Pour cooking liquid into bag; let stand 10 minutes (fat will rise to the top of bag). Seal bag; carefully snip off 1 bottom corner of bag. Drain liquid into bowl, stopping before fat layer reaches opening; discard fat. Add reserved vegetable mixture to liquid.
To prepare polenta, combine water and milk in a large saucepan; bring to a boil, stirring occasionally. Gradually add cornmeal, stirring constantly with a whisk. Cover and cook over medium heat 10 minutes or until thick, stirring frequently. Add cheese and 1 teaspoon salt, stirring until cheese melts.
To prepare gremolata, combine parsley, rind, 1/4 teaspoon kosher salt, and 3 garlic cloves. Serve gremolata over polenta, lamb, and vegetable mixture.
Instead of shanks, we chose shoulder chops (sometimes labeled "arm chops"), which are smaller and easier to handle. Prepare the lamb and vegetable mixture a day in advance; combine the ingredients for the gremolata earlier in the day, and refrigerate until dinnertime.