Place the porcini mushrooms in a bowl and cover with hot water. Let sit for 1 hour, until rehydrated.
In a large pot, heat the olive oil over medium heat. Add the pork and beef and cook, mixing to break into smaller pieces. Pour off the excess fat, then add the celery, carrots and cremini mushrooms and cook until soft. Add the porcini and soaking liquid, tomato sauce and bring to a simmer. Cook for 10 minutes, until flavorful. Adjust the seasoning with salt and pepper. Stir in the peas and remove from the heat.
Meanwhile, bring a large pot of salted water to a boil. Add the bucatini and cook according to package instructions. Drain the pasta, return to the pot, and drizzle with olive oil.
Toss the pasta with the sauce, divide the between plates and top with shaved parmesan.