In a large skillet, add 1 tablespoon of extra virgin olive oil and brown 16oz of Italian sausage over medium heat
While the Italian sausage is cooking, bring a large pot of water to a boil, add a large pinch of salt and cook the penne according the manufacturers directions
Once the Italian sausage is browned and cooked through, transfer it to a bowl and set it aside for now
In the same skillet, cook the diced onions for about 5 minutes before adding the chopped mushrooms and cooking until they are softened and lightly caramelized
Add the finely minced garlic and cook for about 60 seconds, stirring constantly
Transfer the onions, mushrooms and garlic into a bowl and set aside for now
Add 2 cups of chicken stock and 2 cups of heavy cream, increase the heat to medium high and bring the mixture to a simmer
When the pasta is cooked, drain it and add it into the simmering chicken stock and heavy cream mixture
Once the sauce begins to thicken slightly, remove the skillet from the heat and add 1 cup of grated parmesan
Once the parmesan is incorporated, add the browned Italian sausage, onions, mushrooms and garlic, along with 4 ounces of finely shredded parmesan and mix to combine
Garnish with a little extra parmesan and some finely chopped fresh parsley
Serve immediately
Store leftovers in an airtight container in the refrigerator or the freezer