Season and sear the chicken: Pat the chicken dry and season both sides with salt, pepper, garlic powder, and Italian seasoning. Heat olive oil in a large skillet over medium-high heat. Add chicken and cook for 4–5 minutes per side until golden brown and cooked through. Remove and set aside.

Sauté the aromatics: In the same skillet, reduce heat to medium. Add butter, then stir in the chopped onion. Cook until soft and translucent, about 3–4 minutes. Add minced garlic and sauté for another 30 seconds until fragrant.

Deglaze the pan: Pour in chicken broth and stir, scraping up any browned bits from the bottom of the pan. Simmer for 2 minutes.

Make the cream sauce: Lower the heat slightly and pour in the heavy cream. Stir in Parmesan cheese until melted and smooth. Simmer gently for 2–3 minutes.

Add spinach: Stir in the fresh spinach and cook until wilted, about 1–2 minutes. If you prefer a thicker sauce, mix cornstarch with 1 tablespoon of water to form a slurry and stir it into the sauce. Let it simmer for another minute to thicken.

Return the chicken: Add the cooked chicken back to the skillet. Spoon the sauce over the chicken and simmer for 2–3 minutes more until heated through.

Serve: Garnish with chopped parsley and serve warm over pasta, rice, mashed potatoes, or with crusty bread.