Season chicken breasts with salt, pepper, and Italian seasoning.
Heat olive oil in a large skillet over medium-high heat. Sear chicken 4–5 minutes per side until golden and cooked through. Remove and set aside.
In the same skillet, reduce heat to medium. Melt butter, then sauté garlic for 1 minute until fragrant.
Stir in heavy cream and chicken broth. Simmer 2–3 minutes.
Add parmesan cheese and red pepper flakes (if using). Stir until sauce thickens slightly.
Add spinach and stir until wilted, about 1–2 minutes.
Return chicken to the skillet and spoon sauce over the top. Simmer on low for 2–3 minutes.
Garnish with fresh parsley and serve warm.