Chicken Saltimbocca Meatloaf

Name: Chicken Saltimbocca Meatloaf
Ingredients: 3 tablespoons olive oil, divided, or to taste; 6 cups baby spinach; 2 cloves garlic, minced; 1 1/2 teaspoons kosher salt, divided; 1 teaspoon freshly ground pepper, divided; 5 slices prosciutto, thinly sliced; 1 tablespoon unsalted butter; 2 cups sliced mushrooms; 1 pound ground chicken; 1/2 cup almond meal; 1/4 cup grated Parmesan cheese (optional); 1 egg; 1 tablespoon Italian seasoning; 2 cups low-sodium chicken broth; 2 tablespoons arrowroot powder