Season the chicken breasts with salt, pepper, and ½ teaspoon dried Italian seasoning on both sides. In a large skillet, heat one tablespoon of butter and one tablespoon of the oil from the sun-dried tomatoes over medium-high heat and brown the chicken breasts for 4 minutes on each side until completely cooked through. Transfer to a plate.
Add one tablespoon of butter to the same skillet and saute the minced onion, garlic, and sun-dried tomatoes. Add ½ teaspoon of Italian seasoning.
Slowly pour in the chicken broth and heavy cream. Bring to a simmer and add the grated parmesan cheese. Stir until the cheese has melted and add salt and pepper to taste.
Mix in the baby spinach leaves and cook until wilted.
Return the chicken breasts to the skillet and cook until reheated.