How to Make It
Heat the olive oil in a large saucepan until shimmering. Add the onion and garlic and cook over moderately high heat, stirring occasionally, until softened, about 6 minutes. Add the turnips and cook, stirring frequently, until crisp-tender, about 5 minutes. Add the wine and cook until almost evaporated, about 5 minutes. Add the 4 cups of chicken stock and bring to a boil. Reduce the heat to moderately low and simmer until the turnips are tender, about 25 minutes.
Working in batches, puree the soup in a blender or food processor, then strain it through a fine sieve. Return the soup to a clean saucepan, stir in the scallions and cook over moderate heat for 5 minutes. Whisk in the crème fraîche until fully incorporated; thin the soup with stock if necessary. Season with salt and pepper.
Ladle the soup into shallow bowls and serve with the Cheese Crisps.