Prep the chicken: Slice large chicken breasts into cutlets by halving them horizontally. Pat dry.
Season both sides with salt, pepper, and 1 teaspoon Italian seasoning. Lightly dredge in flour if you want a slightly thicker sauce and golden crust.
Heat the skillet: Add olive oil to a large skillet over medium-high heat. When it shimmers, add the chicken in a single layer.
Don’t crowd the pan; work in batches if needed.
Brown the chicken: Sear 3–4 minutes per side, until golden and just cooked through (internal temp 165°F/74°C). Transfer to a plate and tent with foil.
Build the flavor base: Lower heat to medium. Add butter.
Stir in garlic and cook 30 seconds until fragrant. Add sun-dried tomatoes and a pinch of red pepper flakes if using. Stir to coat and warm through.
Deglaze: Pour in the chicken broth.
Scrape up browned bits from the bottom of the skillet. Let it simmer 1–2 minutes to reduce slightly.
Make it creamy: Stir in heavy cream. Bring to a gentle simmer (small bubbles), not a rapid boil.
Add Parmesan and whisk until smooth and slightly thickened, 2–3 minutes.
Season and brighten: Taste and add salt and pepper as needed. Squeeze in lemon juice to balance the richness. Add another pinch of Italian seasoning if you want more herbal notes.
Add the greens: Fold in spinach.
Stir until just wilted, about 30–60 seconds.
Finish the chicken: Return chicken and any juices to the pan. Simmer 1–2 minutes to warm through and coat in sauce. The sauce should be silky and cling to the chicken.
Serve: Garnish with chopped basil or parsley.
Spoon over pasta, rice, mashed potatoes, or crusty bread. Add extra Parmesan at the table if you like.