I first tried this parmesan soup at Chez Nous restaurant in Charleston, South Carolina, and was immediately in awe. This is my version, which has since become a go-to soup for dinners at home, and a trusty addition to my entertaining repertoire. The original is served with lardons and garlic croutons. But as I can’t possibly let things be, I swap the lardons for sautéed mushrooms and add a drizzle of truffle oil for a touch of elegance. This soup is creamy but not thick, incredibly flavorful but not overpowering. If you would like it to be even thicker and richer, you can also substitute half-and-half for heavy cream. I love it as is, with all the bits from the pan, but you can blend or strain it for a smoother texture if you like. Do splurge on real Parmigiano-Reggiano. As it’s the base of the soup, the quality comes …