Prep the chicken. Pat the chicken dry. If using breasts, slice horizontally into cutlets for even cooking.
Season both sides with salt, pepper, and garlic powder. Lightly dredge in flour, shaking off the excess.
Sear the chicken. Heat 1 tablespoon olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add the chicken and cook 3–4 minutes per side until golden and just cooked through.
Transfer to a plate and tent with foil.
Build flavor. Reduce heat to medium. Add a drizzle of oil if needed. Sauté the shallot (if using) for 1–2 minutes until soft.
Stir in the garlic for 30 seconds until fragrant—don’t let it brown.
Add tomatoes and seasoning. Stir in sliced sun-dried tomatoes, 1 teaspoon Italian seasoning, and a pinch of red pepper flakes. Cook 1 minute to bloom the spices.
Deglaze. Pour in the chicken broth, scraping up browned bits from the pan. Simmer 2–3 minutes to reduce slightly.
Creamy base. Lower the heat and stir in the heavy cream.
Let it gently bubble for 2–3 minutes until it thickens. If it feels too thin, simmer a bit longer. If it thickens too quickly, splash in more broth.
Cheesy richness. Stir in the Parmesan until melted and smooth.
Taste and adjust salt and pepper.
Wilt the greens. Add the spinach in handfuls, stirring until just wilted and vibrant.
Return the chicken. Nestle the chicken back into the sauce with any juices. Simmer 2 minutes to warm through and coat. Finish with a squeeze of lemon and a sprinkle of chopped basil or parsley.
Serve. Spoon over pasta, rice, mashed potatoes, or with crusty bread.
Garnish with extra Parmesan and herbs.