A simple roasted vegetable soup gets an upgrade with frico and shaved black truffles.
Heat oven to 450 degrees. Place celery root, parsnips, carrots, beets, potatoes, onion, garlic, rosemary, thyme, and olive oil in a large bowl. Toss to combine.
Transfer vegetable mixture to a baking pan. Roast until tender, about 45 minutes, turning several times during roasting.
Remove the vegetables from oven, and transfer to a large stockpot. Add the chicken stock, 3 cups water, salt, and pepper; bring to a boil. Reduce the heat to medium low, and simmer until the vegetables are very tender, 20 to 30 minutes.
Set a sieve over a large bowl. Pass soup through sieve, reserving liquid. Wipe out the stockpot. Transfer half of the solids to the bowl of a food processor, and add 1 cup reserved liquid. Pulse until pureed. Pass soup through a fine sieve back into the stockpot. Repeat with the remaining solids and liquid. Add the cream, and gently heat soup until hot; season with salt and pepper. Serve soup with frico and shaved black truffles, if using.