Place garlic heads in a small roasting dish and drizzle each half with olive oil and season with salt and pepper. Cover with foil and roast for 45 minutes to 1 hour or until soft. Let cool slightly and squeeze the cloves of garlic into a small bowl.
For the lamb shanks:
Preheat oven to 350 degrees F.
Heat the oil in a large Dutch oven until smoking. Season the shanks on both sides with salt and pepper and sear until golden brown on both sides, remove to a plate. Remove all but 2 tablespoons of the fat in the pan and add the celery, carrots and onions and cook until caramelized.
Add the port and red wine and cook until almost completely reduced. Add the chicken stock, thyme, parsley sprigs and shanks and salt and pepper and bring to a boil on the stove, cover, transfer to the oven and bake for 1 1/2 to 2 hours or until the meat is tender.
Remove shanks to a plate and loosely tent with foil to keep warm. Strain the cooking liquid into a medium saucepan and discard the solids Whisk in the roasted garlic and cook over high heat, whisking occasionally, until reduced by half, 12 to 15 minutes. Remove 1 cup of the liquid to use for the orzo and continue reducing the remaining liquid by half again or until thickened to a glaze. Serve the lamb on top of the orzo and drizzle the shanks with the reduced cooking liquid, oven roasted tomatoes and chopped parsley.
For the orzo pasta:
Heat a medium nonstick pan over medium-high heat. Add 1/2 of the orzo and toast until golden brown.
In a medium saucepan, heat the oil and 2 tablespoons butter over medium heat, add the onion and cook until soft. Add the toasted orzo and the remaining orzo and saute for 1 minute to coat the pasta with the oil/onion mixture. Bring 8 cups of water or chicken stock to a boil in a medium pot (or a combination of chicken stock and water) and add hot water/stock to the orzo as if you were making risotto, 1 cup at a time, stirring constantly until the liquid is absorbed and the pasta is al dente (you may not need to use all of the water). Stir in the cold butter and a 1 cup of the braising liquid, chopped parsley and salt and pepper to taste and cook 1 minute longer.
For the slow roasted tomatoes:
Toss the tomatoes in olive oil, season with salt and pepper and roast in a 200 degree F oven for 6 hours.
Make extra roasted heads to use for garnish on the plate, if desired .