Bring a large pot of generously salted water to a rolling boil for the pasta. Meanwhile, heat 1 tablespoon of olive oil in a large skillet or Dutch oven over medium-high heat.

Add the Italian sausage to the hot skillet, breaking it up with a spoon. Cook for 6-8 minutes, stirring occasionally, until deeply browned and cooked through. Drain off any excess fat, leaving about a tablespoon in the pan, then remove the sausage and set aside.

Reduce heat to medium. Add the remaining 1 tablespoon of olive oil to the skillet, if needed. Add the diced onion and cook for 4-5 minutes until softened and translucent. Stir in the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Pour in the crushed tomatoes and bring the mixture to a gentle simmer. Return the cooked sausage to the skillet. Season with salt and freshly ground black pepper to taste. Let the sauce simmer for 10-15 minutes, stirring occasionally, to allow the flavors to meld and deepen.

While the sauce simmers, add the pasta to the boiling salted water. Cook according to package directions until al dente. Before draining, reserve about 1 cup of the starchy pasta water.

Stir the heavy cream into the simmering tomato sauce. Add about 0.5 cup of the reserved pasta water to loosen the sauce to your desired consistency; add more if needed. Taste and adjust seasoning if necessary.

Drain the pasta and add it directly to the skillet with the sauce. Toss gently to combine, ensuring the pasta is well coated. If the sauce seems too thick, add a splash more pasta water. Stir in the fresh chopped basil.

Serve immediately in bowls, garnished generously with grated Parmesan cheese and an extra sprinkle of fresh basil, if desired.