1. Preheat oven to 400°. Combine first 7 ingredients (through cloves) in a large bowl. Whisk together next 6 ingredients (through oil) in a medium bowl. Make a well in center of dry ingredients; add wet mixture. Stir just until moist.
2. Preheat waffle iron, and coat it with cooking spray. Add about 1/2 cup batter, and spread it to edges; cook until the steaming stops. Repeat with remaining batter, setting waffles aside until all are cooked. Place on baking sheets in oven for 5 minutes to crisp.
3. Melt the butter in a saucepan over medium-low heat. Add walnuts; sauté 3 minutes or until lightly toasted. Add the maple syrup; simmer 2 minutes. Dust waffles with powdered sugar, if desired. Serve with warm syrup.