Preheat oven to 350 degrees
Place parsnips and onion on sheet pan and drizzle with olive oil. Place in oven and roast for about 45 minutes or until golden in parts and able to pierce with a fork.
In a soup pot over medium high heat, saute celery, carrots and garlic in butter until softened, abut 5 minutes.
Add roasted parsnips and onion to soup pot, cover with chicken broth and add thyme sprigs.
Simmer for 30 minutes.
Season with salt and pepper to taste.
Using an immersion blender (pour into regular blender and pulse if not using immersion) blend until fairly smooth. Add cream and simmer for another 5-10 minutes.
Top with crispy fried shallots or chives, bacon, etc.