Preheat oven to 350°F.
Bring a small pot of water to a boil, and add 1/2 teaspoon salt and the spinach.
When spinach wilts, drain in a colander and run cold water over spinach until it is completely cool.
Whisk together cornmeal, buttermilk, egg yolks, the remaining 1/2 teaspoon salt, baking soda, white pepper, butter, nutmeg, and roasted garlic.
In a clean, dry bowl, using an electric hand mixer, beat egg whites until stiff peaks form.
Fold egg whites into cornmeal mixture. Add spinach and stir. Spray a 2-quart baking dish with vegetable spray and add spoon bread batter.
Bake spoon bread 30 minutes, or until lightly browned on top and a toothpick inserted in the center comes out clean.
ROASTED GARLIC: Preheat oven to 300°F; cut the top off the head of garlic, and place both pieces on foil; mix 1 teaspoon water and 1/2 teaspoon olive oil, and drizzle over garlic; sprinkle with coarse salt and freshly ground black pepper; close foil and roast 1 hour, or until garlic cloves ooze from their papery skins; squeeze out the roasted garlic and use as needed.