Prep the chicken: Pat the chicken dry and slice it into thin strips. Season with salt, pepper, and Italian seasoning if using.
This helps the chicken sear quickly and stay juicy.
Sear the chicken: Heat 1 tablespoon oil or butter in a large skillet over medium-high. Add the chicken in a single layer. Cook 3–4 minutes per side until golden and cooked through.
Transfer to a plate and tent with foil.
Soften the garlic: Reduce heat to medium. Add the remaining oil or butter to the same skillet. Stir in the minced garlic and cook 30–60 seconds until fragrant, scraping up browned bits.
Build the sauce: Add the butter and let it melt.
Pour in the heavy cream and bring to a gentle simmer. Don’t boil hard—keep it soft and steady.
Add the cheese: Whisk in Parmesan (and pecorino, if using) a little at a time until melted and smooth. If the sauce seems too thick, whisk in chicken broth a splash at a time until it coats the back of a spoon.
Season: Stir in nutmeg and red pepper flakes if you like.
Taste and adjust salt and pepper. The sauce should be rich, slightly salty, and garlicky.
Combine: Return the chicken and any juices to the pan. Simmer 1–2 minutes, stirring, until coated and heated through.
Serve: Spoon the chicken Alfredo over zucchini noodles, spaghetti squash, sautéed mushrooms, or steamed broccoli.
Garnish with parsley and extra Parmesan.