Boil the pasta: Bring a large pot of salted water to a rolling boil. Cook the high-protein pasta to al dente according to package directions.
Reserve 1 cup of pasta water, then drain.
Season the chicken: Pat the chicken dry. Toss with 1 tbsp olive oil, salt, pepper, and Italian seasoning until evenly coated.
Sear the chicken: Heat a large skillet over medium-high. Add the remaining 1 tbsp olive oil.
Cook the chicken in a single layer for 3–4 minutes per side until browned and just cooked through. Transfer to a plate and tent with foil.
Start the sauce base: Reduce heat to medium. Add butter to the same skillet.
Stir in garlic and cook 30–60 seconds until fragrant, scraping up browned bits.
Build the creaminess: Pour in chicken broth and milk. Whisk in light cream cheese until melted and smooth. Reduce heat to low.
Add the protein boost: Remove the pan from heat for a moment.
Whisk in Greek yogurt until silky. Return to low heat (don’t boil), then stir in Parmesan until melted. If it’s too thick, loosen with splashes of pasta water.
Season and balance: Add red pepper flakes if using and squeeze in lemon juice.
Taste and adjust salt and pepper. The sauce should be creamy, glossy, and well seasoned.
Combine: Toss the cooked pasta and chicken into the sauce. Add a bit of reserved pasta water to help the sauce coat every strand.
Stir in parsley.
Finish and serve: Let everything warm together for 1–2 minutes on low. Serve hot with extra Parmesan and a crack of black pepper.