Season the chicken. Pat the chicken thighs dry.
Sprinkle both sides with salt, pepper, and Italian seasoning. This helps the chicken brown and seasons the sauce later.
Sear the thighs. Heat olive oil in a large skillet over medium-high heat. Add chicken in a single layer and cook 5–7 minutes per side until browned and nearly cooked through.
Transfer to a plate and keep warm.
Sauté aromatics. Lower heat to medium. Add garlic to the pan and cook 30–45 seconds until fragrant. Stir in sun-dried tomatoes and red pepper flakes.
Cook 1 minute to bloom the flavors.
Deglaze with broth. Pour in chicken broth, scraping up browned bits. Simmer 2–3 minutes to reduce slightly. Those bits deepen the sauce’s flavor.
Add the cream and cheese. Stir in heavy cream and bring to a gentle simmer.
Sprinkle in Parmesan, stirring until melted and smooth. Keep heat at a low simmer to prevent curdling.
Return the chicken. Nestle thighs back into the sauce. Simmer gently 5–8 minutes, or until the chicken is cooked through and the sauce thickens to coat the back of a spoon.
Finish the sauce. Stir in spinach until wilted, about 1 minute.
Add lemon juice and taste. Adjust salt and pepper as needed.
Garnish and serve. Top with chopped basil or parsley. Serve over pasta, rice, or mashed potatoes, or with crusty bread to catch the sauce.