This is a very good, refined soup. I used nonfat milk. I liked the walnut oil on it, but also tried another bowl with truffle oil, and that really brought it over the top!
This is a lovely, simple soup with comfort food appeal. I didn't have purple potatoes, but did have the purple cauliflower. My husband prefers some texture to his soups, and I therefore didn't puree until fully smooth. I omitted the drizzle of walnut oil, but served with toasted garlic asiago bread. It was a rainy and cool day, and this was perfect, although unusually colored soup.