To make goat marinade (which should done one day in advance), place goat meat in a bowl with the rosemary, thyme, garlic, and bay leaf. Add wine to reach just below the covering point. Stir, cover, and refrigerate overnight.
The next day, drain and reserve the marinade. Place the meat on a plate and sprinkle with flour. Turn to coat well and set aside.
To make the sauce, heat 2 tablespoons olive oil in a large saucepan over medium heat. Add the onion, carrot, and celery, and stir. Sauté until vegetables are tender and slightly golden. Add the floured goat cubes, pressing down lightly so that they brown evenly on all sides. Once the goat begins to attach to the bottom of the pan, add the reserved marinade and cook until it evaporates.
Add the porcini mushrooms and tomato sauce, and stir well. Cover the goat with beef stock and stir. Cover the pan and reduce the heat to medium-low. Cook for 1 1/2 hours, stirring about every 15 minutes. Add more stock, if necessary, as the sauce cooks down. (You should always have about 1/2 inch stock covering the goat.) The sauce is ready when it is highly aromatic and thickened, yet still quite fluid. Add the salt.
Bring a large pot of water to boil over high heat. Add the pasta and cook until al dente, about 10–12 minutes.
Drain pasta and add to the goat sauce. Combine gently. Add the remaining 2 tablespoons olive oil and serve with grated parmigiano-reggiano.