Heat the olive oil in a large pot or deep skillet over medium heat.
Add the sliced Italian sausage and cook for 5-6 minutes until browned and cooked through. Remove sausage from the pot and set aside.
In the same pot, add the diced onion and cook for 2-3 minutes until softened.
Add the minced garlic and cook for 1 minute until fragrant.
Pour in the chicken broth and water, then add the penne pasta, salt, black pepper, dried oregano, dried basil, and red pepper flakes. Stir to combine.
Bring the mixture to a boil, then reduce heat to medium-low. Cover and simmer for 12-15 minutes, stirring occasionally, until the pasta is cooked and most of the liquid is absorbed.
Return the cooked sausage to the pot and stir to combine.
Stir in the grated Parmesan cheese and heavy cream until the sauce is creamy and well mixed.
Cook for an additional 2 minutes to heat through.
Remove from heat and sprinkle with chopped fresh parsley before serving.