Pre-heat oven to 325 degrees.
Using a small, thick-bottomed rondeau, heat the olive oil and butter over medium high. Season the veal shanks thoroughly with salt and pepper. Coat the veal shanks with flour, shake to remove any excess, and brown well. Remove veal shanks from rondeau.
Make the sachet:
Add the vegetables and the sachet to the pan. Stir to coat and place the veal shanks on top. Add the wine, tomato sauce and stock, adjust the seasoning, and bring the mixture to a boil. Cover and cook the veal shanks in the oven for 1 1/2 hours, or until the meat is very tender.
In a large sauce pot over medium heat, sweat the onion, shallots and garlic in the olive oil.
When vegetables are soft, add the rice and saffron, and salt and pepper to taste. Stir and continue cooking to toast the rice. When the rice is slightly browned, add the wine, stirring constantly.
In a separate sauce pot, bring the chicken stock to a boil. Add the hot stock to the rice in three batches, stirring constantly until the liquid is fully absorbed.
Continue the osso buco : Remove the shanks from the rondeau and reduce the jus to your taste.
Peel an orange down to the flesh. Using a knife, separate each segment from the surrounding membrane and remove. Place segments in a bowl. Squeeze orange halves over bowl to release any remaining juice.
Using a sturdy Japanese mandolin, shave the fennel, white bulb down at an angle. Place fennel in a mixing bowl, and then shave the onion. Add onion to bowl, and toss. Add the juice of 1/2 lemon, the juice from the orange, salt and pepper to taste, and the olive oil. Toss again. Add the orange segments and chives , tossing once more, and serve.
Fold the butter and cheese into the risotto , reserve over low heat.
Pour jus over the shanks, top with gremolata , and serve with saffron risotto.