Bring large pot of salted water to a boil over high heat. Cook pasta according to package directions.
In a large deep skillet over medium-high heat, add olive oil. Add onion, garlic, Italian seasoning mix and red pepper flakes, if using. Sir frequently and cook until the onions are soft and fragrant, about 3 to 4 minutes. Add sausage and cook for 1 minute. Add can of crushed tomatoes, stirring all the ingredients together to combine. Season with kosher salt and freshly ground black pepper, to taste and let simmer for 10 minutes. Stir in heavy cream and mix well.
Drain the pasta and add directly to the skillet with the sauce Toss the pasta to coat with the sauce. Transfer to a serving bowl or platter and garnish with basil leaves. Serve with the cheesy garlic bread.
For the cheesy garlic bread:
Preheat oven to 400 degrees F.
Sprinkle cheese and Italian seasoning over garlic bread half. Place on tinfoil lined baking sheet and cook in the oven for 10 to 12 minutes, until the cheese is melted and bread is warmed through. Slice and serve.
Use the leftover garlic bread from this recipe to make Garlic Bread Pizza.