Preheat the oven to 350°F.
Cut ¼ inch off the tops of the tomatoes. Gently scoop out the pulp, leaving a ¼-inch-thick wall. Be careful not to break the walls or bottom skin. Let drain upside down on a paper towel.
Bring the chicken broth and water to a boil in a medium-size saucepan. Add the orzo slowly, and return to a boil. Reduce heat to simmer and let cook 12 to 15 minutes, stirring occasionally, until the pasta has absorbed the liquid, is firm, and is not sticking together.
In a large sauté pan, warm the oil over medium heat.
Add the onion and cook slowly until soft but not browned, about 8 minutes. Add the garlic and cook about 2 minutes until soft, not browned. Add to the orzo.
Put the sausage in the skillet and sauté over medium heat, stirring constantly and breaking up large pieces until lightly browned. If it seems fatty, drain on paper towels. Let cool slightly. In a medium bowl, combine the sausage and orzo mixture with the oregano, regular Provolone and pine nuts. Stir just until combined. Add salt and pepper to taste.
To assemble: Lightly salt the inside of the tomatoes. Spoon about 1/3 cup of the orzo into each tomato, pressing firmly to fill as much as possible. Place in a casserole dish or pie plate just large enough to hold tomatoes in one layer. Top with the aged Provolone.
Bake for 15 to 20 minutes, or until the tomatoes feel slightly soft to the touch but still hold their shape and the cheese is melted. Sprinkle with parsley.