The recipe, Silky Roasted Yellow Pepper Soup is from the cook book, "Vegetable Soups from Deborah Madison's Kitchen," by Deborah Madison. I chose to use the Vitamix on a low setting to puree the soup and maintain some texture, rather than passing it through a food mill. I added champagne vinegar at the end. The type of vinegar was not specified in the original recipe. I thought of experimenting with Balsamic vinegar, but was afraid it would discolor the beautiful bright color of the soup. I had never broiled peppers in order to later skin them. In the past I had always roasted them at high heat. Broiling was a pleasant revelation and worked well, and I liked Ms. Madison's encouragement to not make yourself too crazy with trying to perfectly skin the peppers. In her notes to the recipe, Ms. Madison advised that you can make a quick version of this soup by just sautéing the peppers and onions, without peeling the peppers. But I agree with her that going the extra steps to roast and peel the peppers is preferred, as the skins of the peppers give a "sharp taste."