In a large, heavy-bottom pot over medium heat sauté the onion, celery, carrot and bay leaf in the olive oil until onion is translucent. Add ground beef, pork, and prosciutto to the sautéed vegetables and use a wooden spoon to break up the meat. When meat is nearly cooked, add tomato paste and stir to fully incorporate. Add white wine and simmer until the wine evaporates. Add the crushed tomatoes and 1/2 can (from the tomatoes) of water.
Bring the sauce to a boil and then reduce to a simmer. Cook, uncovered for approximately 2 hours. Add salt to taste.
Bring a large pot of salted water to a boil.
Cook the tagliatelle until al dente (about 2 minutes less than package directions). Drain, add to the Bolognese sauce and stir to combine. Serve immediately.