Season the chicken: Pat the chicken dry. Season generously with salt, pepper, and half the Italian seasoning. Dry chicken sears better and browns beautifully.

Heat the pot: Set a large, deep skillet or Dutch oven over medium-high heat. Add olive oil and 1 tablespoon butter. When shimmering, add the chicken in a single layer.

Sear in batches: Brown the chicken 3–4 minutes per side until golden. Don’t crowd the pot. Remove to a plate; it doesn’t need to be fully cooked yet.

Sauté aromatics: Lower heat to medium. Add remaining butter. Stir in onion and a pinch of salt. Cook until soft and translucent, about 3 minutes. Add garlic and cook 30–60 seconds until fragrant, not browned.

Deglaze: Pour in chicken stock, scraping up brown bits with a wooden spoon. Those bits add big flavor to the sauce.

Simmer the sauce base: Stir in cream, remaining Italian seasoning, red pepper flakes if using, and a pinch of black pepper. Bring to a gentle simmer; do not boil hard.

Thicken and enrich: Whisk in Parmesan until melted. If you prefer a thicker sauce, stir cornstarch with a splash of cold stock to make a slurry, then whisk it in and simmer 1 minute.

Finish the chicken: Return the chicken and any juices to the pot. Simmer 3–5 minutes until cooked through (165°F internal). Taste and adjust salt and pepper.

Add spinach: Turn heat to low. Fold in spinach by the handful. It will wilt quickly. When just wilted and bright, remove from heat.

Brighten: Add lemon zest and a squeeze of juice. This lifts the richness and makes the garlic sing. Garnish with parsley or basil.

Serve: Spoon over rice, mashed potatoes, or pasta. It’s also great with crusty bread to catch every drop of sauce.