In a large pot over medium-high heat, combine the chopped spinach, vegetable broth, onion, nutmeg, and garlic. Bring to a boil, then lower the heat and simmer for about 10 minutes until the onion is tender.
In a small saucepan, melt the butter over medium heat. Whisk in the all-purpose flour and cook for 2 minutes until the mixture is smooth and free of the raw flour taste. Slowly whisk in the half-and-half and continue cooking until the mixture thickens, about 10 minutes.
Pour the creamy sauce into the pot with the spinach base. Stir thoroughly and let the soup simmer for a few more minutes. Add extra broth if it needs thinning. If preferred, blend the soup using an immersion blender. Season with salt and pepper to taste, then serve hot. Enjoy with crusty bread if you like.