Cook the pasta: Bring a large pot of salted water to a boil. Cook the high-protein pasta until just shy of al dente. Reserve 1/2 cup pasta water, then drain and set aside.

Prep the chicken: Pat chicken dry. Slice into thin cutlets or 1-inch cubes for faster, even cooking. Season all sides with salt, pepper, and Italian seasoning.

Sear the chicken: Heat 1 tablespoon olive oil in a large skillet over medium-high. Add chicken in a single layer. Cook 4–6 minutes, turning once, until golden and cooked through. Remove to a plate and tent with foil.

Sauté aromatics and veggies: In the same skillet, add remaining olive oil and butter. Add diced onion and a pinch of salt. Cook 3 minutes until softened. Stir in minced garlic for 30 seconds, then add broccoli florets. Sauté 3–4 minutes until bright and crisp-tender. Fold in spinach to wilt. Transfer veggies to the plate with chicken.

Build the lighter Alfredo base: Whisk cornstarch into cold milk until smooth. Pour chicken broth into the skillet, scraping up browned bits. Add the milk-cornstarch slurry and bring to a gentle simmer, whisking until slightly thickened, about 2–3 minutes.

Finish the sauce: Reduce heat to low. Whisk in Parmesan until melted and smooth. Remove the pan from the heat and whisk in Greek yogurt until creamy. Season with salt, black pepper, onion powder, and red pepper flakes if using. Add a squeeze of lemon juice and a little zest for brightness.

Combine: Return chicken and veggies to the pan along with the cooked pasta. Toss gently until everything is coated. If the sauce seems thick, loosen with a splash of reserved pasta water. Taste and adjust salt and pepper.

Portion: Divide into 4–5 airtight meal prep containers. Top with chopped parsley and extra Parmesan if you like.