Heat a large Dutch oven over medium-high heat. Coat pan with cooking spray. Add onion, ginger, cumin, and garlic cloves; sauté 5 minutes or until lightly browned. Stir in cider, bourbon, syrup, pumpkin, and broth; bring to a boil. Reduce heat, and simmer 10 minutes.

Place half of pumpkin mixture in a blender; process until smooth. Pour pureed mixture into a large bowl. Repeat process with remaining pumpkin mixture. Return pureed mixture to pan. Stir in milk, flour, salt, and pepper; cook until thoroughly heated (do not boil), stirring frequently. Serve with sour cream. Garnish with parsley, if desired.