Pan-sear the chicken in the same skillet you'll prepare the sauce in, so be sure to choose a larger skillet. At this point, I like to get my pasta water on the stove over high heat, being sure to salt the water.
Cook the chicken in an oiled skillet over medium-high heat for a few minutes on each side, until cooked through. Transfer the chicken to a plate and tent with foil to rest before dicing.
Reduce heat to medium and, in the same skillet, add butter and allow it to melt. Then add the garlic and cook until fragrant. Then add in cream and half-and-half, followed by the buffalo sauce, Italian seasoning, and pepper.
Add 1/2 cup grated Parmesan cheese to the sauce. Whisk it to combine and allow it to simmer to thicken while you cook the noodles. Taste and adjust salt and pepper as needed.
Into the boiling salted water, add your fettuccine noodles and cook them al dente. Use a large slotted spoon or skimmer to transfer the noodles from the water directly into the alfredo sauce.
Add 1/3 cup of pasta water to the sauce along with the pasta. Add in diced chicken and toss well until everything is evenly coated. Top with the remaining 1/4 cup parmesan cheese and minced parsley before serving.