In a large pot, heat the oil. Add the white and tender green parts of the scallions, along with the leeks, fennel and onion; season with salt and white pepper. Cook over low heat, stirring, until the vegetables begin to soften, 15 minutes. Add the wine and boil over high heat until reduced to a few tablespoons, 12 minutes. Add the water and cream and bring to a simmer. Cook until the vegetables are very tender and pale green, 15 minutes. Add the scallion green tops and cook just until softened, 2 minutes.

Working in batches, puree the soup in a blender and return it to the pot. Season with salt and white pepper.

In a medium bowl, whisk the buttermilk with the goat cheese. Ladle the soup into shallow bowls, drizzle with the creamed goat cheese and serve.

The soup and creamed goat cheese can be refrigerated separately overnight. Reheat the soup before serving.