Pat the chicken breasts dry and sprinkle all seasonings evenly on both sides, pressing gently into the meat.

Heat olive oil in a large skillet over medium-high heat. Place seasoned chicken in the hot oil and cook undisturbed for 6-7 minutes. Flip and cook for another 6-7 minutes until internal temperature reaches 165F. Transfer to a cutting board to rest.

Bring a large pot of salted water to a boil. Add spaghetti and cook according to package directions, usually 9-11 minutes. Reserve about 1 cup of pasta water before draining.

In the same skillet used for chicken, melt butter over medium heat. Add minced garlic and Italian seasoning, stirring constantly for about 1 minute until fragrant.

Pour in heavy cream slowly while stirring. Reduce heat to medium-low and add cheddar and parmesan cheeses a handful at a time, stirring after each addition until fully melted and smooth.

Slice the rested chicken breasts into strips. Add drained spaghetti to the sauce and toss gently. Fold in sliced chicken and sprinkle with parsley flakes. Season with salt and pepper to taste. Add reserved pasta water if sauce is too thick.