Preheat your oven to 200 C. Lightly grease a 9x13 baking dish with butter.
Season chicken with Italian seasoning, salt and pepper, to taste. Melt 2 tablespoons butter in a large skillet over medium high heat. Add chicken, skin-side down, and sear both sides until golden brown, about 2-3 minutes per side, set aside.
Melt remaining 1 tablespoon butter in the skillet. Stir in spinach and cook, stirring occasionally, until it begins to wilt, about 2 minutes; set aside. If using frozen, just thaw and squeeze out the water.
To make the garlic Parmesan cream sauce, melt butter in the skillet over medium heat. Add garlic, and cook, stirring frequently, until fragrant, about 1-2 minutes. Whisk in flour until lightly browned, about 1 minute.
Gradually whisk in chicken broth, thyme and basil. Cook, whisking constantly, until incorporated, about 1-2 minutes. Stir in cream and Parmesan until slightly thickened, about 1-2 minutes. If the mixture is too thick, add more milk as needed; season with salt and pepper, to taste.
Place chicken in a single layer into the prepared baking dish. Ass potatoes to the sides and top, then add spinach, and the cream sauce.
Bake until completely cooked through, juices run clear, about 25-30 minutes. Garnish with fresh chopped parsley, serve.