Bring a large pot of salted water to a boil. Cook fettuccine according to package instructions until al dente. Drain and set aside, reserving ½ cup pasta water.

Season chicken breasts with salt, black pepper, and Italian seasoning.

Heat olive oil in a large skillet over medium-high heat. Cook chicken 5–6 minutes per side until golden brown and cooked through. Remove and rest 5 minutes before slicing.

In the same skillet, reduce heat to medium. Add butter and garlic, cooking 1–2 minutes until fragrant.

Pour in heavy cream and stir to combine. Gradually add parmesan cheese, stirring until smooth. Season with salt, pepper, and optional red pepper flakes.

Add cooked pasta to the skillet and toss to coat evenly. Add reserved pasta water if needed to loosen sauce.

Arrange sliced chicken on top of pasta and gently toss to combine.

Plate pasta in bowls. Garnish with chopped parsley and extra parmesan. Serve immediately.