Heat saucepan coated with cooking spray over medium heat. Add fennel and onion, and sauté 8 minutes. Stir in garlic, and cook 30 seconds. Add 1/2 cup wine, and simmer 2 minutes. Add split peas, 1/2 tsp. fennel seeds, thyme, bay leaf, and 7 cups water. Bring to a boil, reduce heat to medium-low, cover, and simmer 50 minutes, stirring occasionally.
Add remaining 1/2 cup wine, and cook, uncovered, 10 minutes, or until split peas are tender. Stir in spinach, and cook 2 minutes, or until spinach is wilted.
Remove bay leaf, and purée soup with immersion blender until smooth. Season with salt and pepper, if desired. Toast remaining 1/2 tsp. fennel seeds in small skillet 2 minutes, or until fragrant. Serve soup garnished with toasted fennel seeds.