Season chicken on both sides with salt, pepper, and paprika.
Heat olive oil in a large skillet over medium-high heat. Sear chicken until well browned, 4–5 minutes per side. Transfer to a plate.
Lower heat to medium. Melt butter in the same skillet, then sauté garlic until fragrant, about 30 seconds.
Whisk in flour and cook 30 seconds to form a light roux.
Slowly whisk in chicken broth. Simmer until slightly thickened, 2–3 minutes.
Stir in heavy cream, Parmesan, and Italian seasoning. Simmer until smooth and creamy, 2 minutes.
Fold in spinach and cook just until wilted.
Nestle chicken and any juices back into the skillet. Simmer gently until cooked through, 5–7 minutes.
Finish with lemon juice and parsley. Taste and adjust seasoning, then spoon sauce over chicken to serve.