To prepare the osso buco recipe, you'll need: 1 pound (240 g) Italian sausage, 2 tablespoons (60 ml) olive oil, 1 teaspoon salt, and 1 tablespoon pepper. Heat the oil in a large skillet over medium-high heat. Add the sausage and cook until browned on all sides, about 5 minutes. Remove the skillet from the heat and add the onion and garlic. Cook, stirring frequently, until the onions are translucent and the garlic is fragrant, 3 to 4 minutes more. Stir in the tomato paste and salt and pepper to taste. Simmer the mixture, covered, for 1 to 2 hours or overnight.