Cook the Rice: In a medium saucepan, bring the vegetable or chicken broth to a boil. Add the rice, reduce heat to low, cover, and simmer for 15 minutes or until the rice is fully cooked. Fluff with a fork and set aside.
Preheat Oven: Preheat your oven to 375°F (190°C) and lightly grease a baking dish.
Sauté Spinach and Garlic: In a large skillet, heat the olive oil over medium heat. Add the minced garlic and cook for 1 minute until fragrant. Add the chopped spinach and cook for 2-3 minutes until wilted. Remove from heat.
Mix Ingredients: In a large mixing bowl, combine the cooked rice, sautéed spinach, Parmesan cheese, sour cream, milk, salt, pepper, and nutmeg. Mix until well combined.
Transfer to Baking Dish: Pour the mixture into the prepared baking dish and spread it evenly.
Add Cheese Topping: Sprinkle the shredded mozzarella on top. For extra crunch, add breadcrumbs if desired.
Bake: Bake for 20-25 minutes, or until the cheese is melted and bubbly. If you prefer a golden crust, broil for an additional 2-3 minutes.
Serve: Let the dish cool for a few minutes before serving. Garnish with extra Parmesan or fresh herbs if desired.