When preparing the veggies for this recipe, peel the parsnips with a swivel peeler and save the peels for later use. Peel the celeriac with a paring knife before dicing.
Warm a tablespoon of olive oil in a soup pot over medium heat. Add the diced onion and cook for a few minutes until fragrant. Stir in the garlic, salt, and pepper and cook for a few more minutes.
Add the parsnips, celeriac, and maple syrup (if using) to the pot. Pour in the vegetable broth, and increase heat to bring to a boil. Reduce heat to maintain a simmer, cover, and cook for 15 minutes until the veggies are tender.
In the meantime, heat the rest of the olive oil in a skillet over medium heat. Once warm, add the sage leaves in a single layer. Let them fry for 30 to 60 seconds until crispy. Transfer them from the pan to a plate lined with a paper towel. Add the parsnip peels to the skillet and cook for a few minutes until crispy. Transfer to the plate with the sage.
When the soup is finished cooking, turn off the heat. Blend it with an immersion (handheld) blender until smooth. See notes for instructions on using an upright blender. Stir in the whole milk.
Ladle the soup into bowls, and top with the crispy sage and parsnip peels. Enjoy!
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