Preheat your Firehawk Kamado Grill to 163°C/325°F for indirect cooking. Season the flour with salt and pepper, then dredge the Ossobuco veal shanks lightly in flour, shaking off any excess
In a Dutch oven, heat olive oil over medium-high heat on the grill's grate. Brown the veal shanks on all sides, about 3-4 minutes per side. Remove and set aside.
In the same pot, add chopped onion, minced garlic, rosemary, thyme, carrots, celery, and Italian parsley. Sauté until softened, about 5-7 minutes.
Pour in red wine (or white wine) to deglaze the pot, scraping up any browned bits from the bottom. Allow the wine to simmer and reduce by half.
Return the browned veal shanks to the pot. Add passata sauce and chicken stock. Bring to a simmer.
Once simmering, cover the pot and transfer it back to the grill. Cook for 2-3 hours, or until the veal is fork-tender, checking occasionally to ensure it doesn't dry out. Adjust grill temperature as needed to maintain a steady cooking temperature.
While the Ossobuco cooks, prepare the polenta. In a separate pot bring 1 liter of water to a boil. Slowly whisk in polenta, stirring constantly to prevent lumps.
Reduce heat to low and continue to cook the polenta, stirring frequently, until thickened, about 20-25 minutes.
Once the polenta is thick and creamy, stir in butter, Parmesan cheese, salt, and pepper to taste.
In a small bowl, combine chopped flat-leaf parsley, finely chopped garlic, and lemon juice to create a gremolata.
Serve the Ossobuco hot from the grill, spooning the sauce over each veal shank. Garnish with gremolata and serve alongside the creamy Parmesan polenta.