1. Bring first 4 ingredients to a boil in a covered large Dutch oven.
2. While broth mixture comes to a boil, place potato-vegetable blend in a microwave-safe bowl. Cover with heavy-duty plastic wrap; vent. Microwave at HIGH 5 minutes. While frozen vegetables cook, add garlic and next 4 ingredients to broth mixture; cover and continue to cook.
3. Using kitchen shears, snip cooked potato-vegetable blend into bite-sized pieces. Stir potato-vegetable blend, spinach, and milk into broth mixture. Cover and cook over high heat 5 minutes or until carrot is tender. Sprinkle with additional black pepper before serving, if desired.