Preheat your oven to 400°F (or 204°C) and oil a rimmed baking dish—season chicken thighs with Italian seasoning, salt and pepper.
Do not pre-cook the gnocchi. Add it directly to the baking dish—it will cook in the sauce as it bakes.
Melt one tablespoon of butter in a large skillet over medium heat. Sear chicken on both sides until golden brown, about 2-3 minutes per side; drain and set aside.
Melt the remaining 1 tablespoon butter in the same skillet. Stir in chopped spinach and cook, stirring occasionally, until it begins to wilt, about 2 minutes. Leave the spinach in the pan and proceed with the sauce.
In the same skillet, melt the remaining 2 tablespoons butter over medium heat. Add minced garlic and cook until fragrant, about 1–2 minutes. Gradually whisk in chicken broth and Italian seasoning. Cook, whisking constantly, about 1–2 minutes. Stir in heavy cream and shaved parmesan cheese until slightly thickened. Adjust seasoning with salt and pepper to taste.
Arrange chicken in the prepared baking dish. Top with uncooked gnocchi and cream sauce. Roast until the chicken is thoroughly cooked, about 25–30 minutes. Serve hot, garnished with parsley.