01 - Preheat oven to 400°F. Arrange parsnips, onion, carrot, and celery on a baking sheet.
02 - Drizzle vegetables with 1½ tbsp olive oil, sprinkle with salt, pepper, thyme, and nutmeg. Toss to coat evenly.
03 - Place garlic head cut side up on a small piece of foil. Drizzle with remaining olive oil, wrap loosely, and place on the baking sheet.
04 - Roast vegetables and garlic for 30 to 35 minutes until parsnips are golden and tender and garlic is soft.
05 - Transfer roasted vegetables to a large saucepan. Squeeze roasted garlic cloves from their skins and add to the pot.
06 - Pour in the vegetable broth. Bring to a boil, then reduce heat and simmer for 10 minutes.
07 - Use an immersion blender or work in batches with a countertop blender to blend the soup until smooth and creamy.
08 - Stir in the cream and gently heat through. Adjust seasoning to taste. Ladle into bowls, garnish as desired, and serve hot.