Make the filling first. Heat the oil in a heavy-based frying pan over a low heat. Add the onion and garlic. Cook, stirring frequently, for 6–7 minutes until soft and translucent. Add the meat and prosciutto, and cook over a medium heat, breaking up and stirring frequently, for 10 minutes until the meat is cooked. Add the parsley and wine and cook until the liquid has evaporated. Cool and transfer to a food processor or blender with the remaining filling ingredients. Season and blend to a coarse paste.
Cut the lasagne sheets into 8 cm (3½ inch) squares and place a nutmeg-sized ball of filling in the centre of each square. Brush a little water around the edges of the squares, then fold the dough over the filling to make triangles. Gently but firmly push down around the filling, sealing the pasta and ensuring that no air has been trapped. Bring the corners on the longest edge of the triangles together, and pinch tightly to seal. Set aside on a baking sheet lightly dusted with semola di grano duro, and cover with a clean tea towel.
Put the stock in a large saucepan, and season with a little salt. Add the tortellini, diced tomatoes and basil, and cook for 2–3 minutes until al dente. Serve the tortellini in warm bowls with the broth, and grated Parmesan.