Preheat the oven: preheat the oven to 180°C / 350-375°F / Gas Mark 4-5.
Season beef: use kitchen tongs to place beef onto chopping board in one flat layer. Season both sides with salt and pepper.
Sear: add olive oil to pan, turn heat to high, place beef into the pan and sear for at least 3 minutes each side to brown the meat. Once browned, remove and transfer to a chopping board with layer of paper towel.
Vegetables: without rinsing the pan, add carrot, onion and celery, fry for 2 to 3 mins on high heat. Then add the garlic and oregano, stir to combine and allow to cook for a further 2 to 3 mins.
Sauce: add the tomato paste and diced tomatoes to the pan. Turn the heat to low and allow the dish to simmer.
Beef: use kitchen tongs to place the browned beef shanks back into the pan on top of the tomato vegetable mixture. Crush the bouillon cubes with your fingers and sprinkle into the pan also.
Stock and wine: pour in the wine, followed by the beef stock. Place the bay leaves in the middle of the dish.
Oven bake: place a lid on the pan and transfer to the middle shelf in the oven. Cook for 1 hour 30 mins. You can remove during this time at 30 minute internals, place on a heatproof surface and use tongs to rotate the beef to the other side.
Gremolata: add the finely chopped parsley, lemon zest and minced garlic to a small bowl and use a teaspoon to stir and combine.
Polenta (optional): cook the polenta according to the packet instructions, in a pan on the stove, add 2 teaspoons of butter and stir to combine.
Serve: portion the polenta onto plates. Place the beef osso bucco onto a heatproof surface in the centre of the table and provide serving utensils.
Garnish: place the gremolata in a small bowl on the table for garnish, alternatively provide finely chopped parsley and cracked black pepper for serving. Enjoy!