Heat oven to 375°F.
In a food processor chop the onion, garlic, and pancetta. Add the ground chicken and pork and process for a few seconds. Add the Parmigiano Reggiano, egg, cream, salt and pepper and blend a few seconds more. Transfer the contents of the food processor to a cold metal bowl. With a spatula, fold in the pistachios. Keep the mixture in the refrigerator until you are ready to make the cannelloni.
Cut the pasta sheets in half, they should be at least four by six inches. Bring a large pan of water to a boil, add 3 tablespoons of salt and cook the pasta sheets for 3 to 4 minutes. You want to soften them, but not overcook them. Drain, then lay them on a wet tea towel. Sprinkle with some water, cover with another wet tea towel before adding a second layer of pasta to prevent them from sticking.
Put 1 ½ cups Simple Tomato Sauce in the bottom of a large casserole dish (9- x 14-inches).
To make your cannelloni, take a fresh pasta sheet, put it on your work surface and with a towel or paper towel pat it dry. With a spatula, spread about ¼ cup of the chicken mixture over the middle of the pasta sheet, leaving one inch at the top and bottom. Roll up in jelly-roll style. Transfer the rolled cannelloni to the casserole. Repeat with the other sheets.
Cover the cannelloni with the Parmesan Cream Sauce and top with a few scattered dollops of tomato sauce. Cover with aluminum foil. Bake for 45 minutes, then remove the foil and bake for 15 more minutes.