Preheat the oven to 325°. Place the cloves, fennel and bay leaves on a piece of cheese cloth and tie into a little pouch with a piece of kitchen string. Set aside. Tie the rosemary and thyme with another piece of kitchen string and set aside.
With a paper towel, pat dry the veal shanks. In a small bowl, mix 1/2 teaspoon kosher salt with the pepper. Sprinkle both sides of the veal with salt and pepper. In a large dutch oven, heat the olive oil over medium - medium-high high heat. Place the veal in the dutch oven and brown on each side. Transfer the veal to a plate and set aside.
Add the mushrooms, onions, celery, leeks and garlic. Sprinkle with 1/2 teaspoon salt and cook over medium heat, until the vegetables give up some of their liquid and begin to soften, about 5 minutes. Stir in the tomato pasted mushroom powder and cook for another minute. Add the wine, bring to a boil and cook for 2-3 minutes then add the stock or broth and bring to a boil. Reduce heat and simmer with the lid off the pan for 5-8 minutes or until the liquid is reduced by about a quarter.
Place the bouquet garni and the herb bundle into the vegetable mix and push down into the liquid. Add the veal shanks back to the dutch oven along with any juices accumulated on the plate. Cover the pot with the lid and place in the oven for 2 1/2 hours or until meat is tender and falling off the bone.
Meanwhile, assemble the gremolata in a small bowl, combine the garlic, lemon zest and parsley and toss with your fingers.
When Osso Bucco is finished, sprinkle each serving with a bit of the gremolata.
NOTE: To make mushroom powder, place dried mushrooms (I used porcini) in a spice grinder or clean coffee grinder and pulse until it forms a powder. Store mushroom powder in an airtight container.