Place a large pot of water on the stove over high heat. Season the water with salt until the water has the saltiness of the ocean.
Re-hydrate the Porcini mushrooms by bringing white wine to a boil and pour over mushrooms. Let the mushrooms soak for about 15 minutes or until tender. Once the mushrooms are tender take them out of the liquid, squeezing gently to remove excess liquid, and reserve the liquid. Chop the Porcini the same size as the Cremini and mix them together.
In a large sauté pan, sauté the onion, mushrooms & pancetta in the olive oil until cooked through and lightly caramelized. Once the mushroom & onion mixture is ready add the cream and the reserved mushroom liquid. Turn the heat to high and bring to a boil. Remove from heat and add butter and season with salt and pepper to taste.
When the water reaches a boil, add the pasta, being careful not to stir or disturb the pasta. This will help avoid breaking the pasta. When the pasta is ‘al dente’ drain off the water and add the pasta to the Ragu. Return the Ragu to heat and continue cooking for another 30-60 seconds. Add the parsley and toss.
Divide between four pasta bowls and grate Parmigiano-Reggiano over each.
Serve immediately.