Cook the fettuccine according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
In a large skillet, heat the olive oil over medium heat. Add the Italian sausage and cook until browned, breaking it up with a spoon, about 5-7 minutes.
Add the minced garlic to the skillet and sauté for an additional 1-2 minutes until fragrant.
Pour in the heavy cream and stir to combine. Bring to a simmer, then reduce heat to low.
Stir in the grated Parmesan cheese and Italian seasoning, mixing until the cheese is melted and the sauce is creamy. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.
Season with salt and pepper to taste. Add the cooked fettuccine to the skillet and toss to coat the pasta evenly with the sauce.
Serve immediately, garnished with chopped parsley.