Season both sides of chicken with ½ teaspoons of salt and ¼ teaspoon of black pepper, then dredge in flour and shake off the excess.
Heat olive oil and 1 tablespoon of butter in a large skillet over medium heat. Cook chicken 4–5 mins per side until golden and cooked through. Set aside.
In the same skillet over medium heat, add butter and shallots. Sauté 2 mins, then add garlic and cook 30 secs until fragrant.
Pour in wine, Italian seasoning, and chicken stock. Stir, scrape up browned bits, and simmer 3–4 mins over medium-high heat.
Add heavy cream to the skillet. Stir and let it simmer for 2-3 minutes over medium heat. Let the sauce thicken slightly.
Stir in Parmesan until melted. Add spinach and simmer 1-2 minutes, until just about to wilt.
Return chicken to the skillet. Spoon creamy spinach sauce over top and simmer 4-5 minutes, until heated through and flavors combine.
Refrigerator: Store leftover Chicken Florentine in an airtight container in the fridge for up to 3 days. Keep the chicken and sauce together, or separate if you want to maintain the best texture.
Freezer: You can freeze Chicken Florentine, but the creamy sauce may separate slightly when thawed. If freezing, let it cool completely first, then place it in a freezer-safe container for up to 2 months. For best results, freeze the chicken and spinach sauce separately.