Heat oil in a medium Dutch oven over high heat until smoking. Season the shanks on both sides with salt and pepper and sear until golden brown on both sides. Remove shanks to a plate. Add the celery, carrots, and onions and cook until caramelized. Add the Port and red wine and reduce by half. Add the chicken stock, the pulp from the roasted garlic, and return the shanks; bring to a boil on the stove, and then cover and bake in the oven for 2 hours or until tender. Remove shanks, strain sauce into a medium saucepan, and reserve 1 cup of the braising liquid for cooking the orzo. Cook the sauce over high heat until liquid is reduced by half. Serve shanks with sauce, orzo, and tomatoes.
Bring 8 cups of water (or a combination of chicken stock and water) to a boil.
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 butter and oil over medium heat, then 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 onion mixture. Add hot water to the orzo as if you were making risotto, a little at a time, until the pasta is al dente. Finish with the cold butter and 1 cup of the braising liquid. Stir in parsley and season with salt and pepper, to taste.
Preheat oven to 200 degrees F.