Combine flour, salt and pepper in a large bowl. Lightly coat Osso Bucco in flour, shaking off any excess.
Heat oil in a heavy pot (Dutch Oven). Working in small batches, brown the Osso Bucco and place on a plate.
Add a bit more oil into pot and saute the carrots and celery for 5 minutes.
Mix in pureed tomatoes mix and chopped fresh tomatoes. Add white wine and beef stock.
Place Osso Bucco into the pot, cover with lid allow to simmer.
After cooking for 1 hour, add splash of balsamic vinegar and top up with extra beef stock if needed (add enough to keep meat well covered. Cover and cook for another 30-60 minutes until fork tender.
Remove Osso Bucco with a slotted spoon, cover with foil and keep warm. Bring remaining liquids to a healthy simmer on medium heat until it reduces (at least 15 minutes).
Serve over Mashed Potatoes, Polenta or Pasta. Garnish with a generous sprinkle of Gremolata.