Set the oven to 400°F and lightly grease a 9x13 inch baking dish with oil or spray.
Season the chicken thighs evenly with Italian seasoning, salt, and pepper.
Heat 2 tablespoons of butter in a large skillet on medium-high heat, then add chicken skin-side down and brown for 2-3 minutes on each side until golden, then remove from heat.
In the same skillet, melt the remaining 1 tablespoon butter, add the chopped spinach and sauté for about 2 minutes until wilted, then set aside.
Arrange the seared chicken in a single layer in the prepared baking dish, then layer the halved potatoes and sautéed spinach on top.
Prepare the garlic parmesan cream sauce by melting ¼ cup butter in the skillet over medium heat, adding minced garlic and cooking for 1-2 minutes until fragrant.
Whisk in the flour and cook until lightly browned, about 1 minute.
Slowly whisk in chicken broth, dried thyme, and dried basil, cooking and stirring for 1-2 minutes to combine.
Stir in half and half and Parmesan cheese, letting the sauce thicken slightly for 1-2 minutes; add extra half and half if it’s too thick, then season with salt and pepper.
Pour the garlic parmesan cream sauce evenly over the chicken, potatoes, and spinach in the baking dish.
Roast everything in the oven for 25-30 minutes until the chicken reaches an internal temperature of 165°F and potatoes are tender.
Remove from the oven and sprinkle with fresh parsley before serving immediately.
