Combine the olive oil, vinegar, rosemary, parsley, garlic, and salt and pepper and mix well to form a basting marinade.
Make small slits over the surface of the leg of kid goat and insert slivers of garlic and sprigs of parsley into each slit. Roast slowly over an indirect fire, basting frequently, until the meat reaches an internal temperature of 155°F [68°C], about one hour.
Allow the meat to rest at least 20 minutes. Pull the meat from the bone and reserve the meat for the ravioli filling. (The kid goat can be roasted one day in advance. Consider roasting a whole kid goat and freezing the remainder for later use.)
Heat the olive oil over medium-high heat in a nonstick skillet and brown the pulled meat. Remove the meat with a slotted spoon and drain. Reserve.
Reduce the heat to medium, add the onions, and cook just until translucent. Add the garlic and cook for 30 seconds. Deglaze with the wine and stir in the tomato paste.
Return the meat to the pan and add the demi-glace and stock. Add the bay leaf and season with salt and pepper. Increase the heat to a boil, then reduce the heat to a low simmer. Cover and cook for 2 to 3 hours, adding water as needed, or until the meat is very tender and the onions have dissolved and thickened the sauce. Reserve warm for service. (The sauce can be made one day in advance and refrigerated or frozen for later use.)
Sift the flour and salt together on a clean surface or in a large bowl. Form it into a mound with a well in the center.
Break the eggs into the well and using your fingertips, draw the flour into the eggs until the eggs are incorporated and a dough is formed. Using the heels of your hands, knead the dough on a floured surface for 5 minutes, or until a smooth, elastic dough is formed. The dough can be made in a processor by first adding the flour to the bowl. With the processor running add the eggs, one at a time, and process until incorporated. Pulse to form a smooth dough. Remove to a floured surface and knead by hand 1 minute.
Divide the dough into 4 parts. Roll the pasta into thin sheets using a pasta rolling machine.
Chop the garlic slivers and parsley from the roasted meat and mix with the shredded meat, sage, and cheese. Season with salt and pepper.
Starting near the end of 1 sheet of pasta, place 1 teaspoon [5 mL] of filling 2 inches [5 cm] apart along its length. With a pastry brush dipped in water or beaten egg, lightly moisten the area around the mounds of filling. Take a second sheet of pasta and carefully place it over the top of the sheet with the filling. Press firmly around each mound to seal, being careful to remove any air pockets.
Using a pastry wheel, cut 2-inch [5-cm] square ravioli. Place the ravioli on a sheet pan that has been dusted with flour or cornmeal. Do not allow the ravioli to touch. Repeat with the remaining sheets of dough.
Bring 6 quarts [6 L] of lightly salted water to a slow boil and cook the ravioli in batches for 5 to 6 minutes, or until they rise to the surface and the edges are cooked. Remove the ravioli with a slotted spoon to a large bowl. Toss with some of the sauce to prevent sticking. (This also flavors the pasta.)
Serve each person 3 ravioli, topped with sauce and garnished liberally with the Parmesan and black pepper.