In a skillet or deep frying pan, heat the olive oil over medium heat. Add the chopped onion and sauté until it starts to soften. Add the sausage meat to the pan. Cook, stirring frequently, until the sausage is slightly browned.

Add the chopped radicchio to the sausage and onion and mix. Also, add salt and pepper to taste. Continue cooking on a low heat until all the radicchio has wilted.

Bring a large pot of water to a boil. Add salt once it boils and bring it to a boil again. Cook the pasta al dente according to the package instructions. Reserve a cup of pasta cooking water before draining.

Meanwhile, mix in the heavy cream to the sausage and radicchio, then simmer for about 5 minutes. If the sauce appears dry, stir in some reserved pasta cooking water to adjust consistency.

Add the drained pasta to the sauce in the skillet. Toss to combine everything thoroughly and cook together for an additional 2-3 minutes. Adjust the sauce's consistency with pasta water if needed.

Garnish with chopped fresh parsley and serve hot.