Prep: Thoroughly wash the spinach. Peel and dice the onion. Peel and mince the garlic. Use whole nutmeg freshly grated with a Microplane when possible. Like many whole spices, nutmeg dies a pretty quick death when ground before it's needed. It's important to cook your roux, or you'll end up with a raw-flour taste in your spinach. This bechamel sauce is a classic French mother sauce, the basis for many sauces and dishes, including mac and cheese and fondue. The darker the roux, the more nutty and intense the flavor it will give a sauce. Here the roux doesn't need to be cooked further than a light, or blond, color. Serve with grilled steak, chicken or just about any grilled or roasted meat.