Remove veal shank meat from the bone and cut into 1/2-inch pieces; season with 1 tsp salt and 1 tsp pepper. Heat oil in rondo. Add shank meat; brown evenly. Remove veal from pan and set aside; pour off drippings.
Melt 1/2 cup butter in rondo; add onions and carrots. Sauté until onions are golden brown. Sprinkle flour over vegetables; stir well. Cook 2 to 3 minutes. Deglaze pan with wine and tomato paste and reduce to au sec. Stir in stock; return veal to pan. Bring to a boil; cover tightly. Braise in 325°F oven 1-1/2 to 2 hours or until veal is fork-tender.
Remove veal from pan; divide evenly among twelve 16 ounce baking dishes; cover and set aside. Strain braising liquid into large saucepan. Simmer until reduced to 4 cups and sauce is syrupy and clarified but not too intense, skimming surface as needed. Season with salt and pepper.
Ladle 3 oz sauce into each baking dish. Cover and let cool.
Top each baking dish with 1 cup mashed potatoes, spreading to cover entire surface. Sprinkle each with 1 Tbsp Sartori Fontina Cheese. Cover and refrigerate until ready to serve.
For Parmesan Mashed Potatoes: Add 1 Tbsp salt and potatoes to boiling water. Cook until potatoes are fork-tender; drain. Place potatoes in mixer bowl. Mix on low speed, adding milk, 3/4 cup butter and Sartori Parmesan Cheese, until smooth. Season with salt and pepper.