When I started writing A Serious Bunburyist, I penciled out a list of five favorite recipes that I wanted to cover: Fergus Henderson’s Beetroot, Red Onion, Red Cabbage, CrèmeFraîche and Chervil Salad; Richard Olney’s Potato and Leek Soup; and Paul Bertolli’s Cauliflower Soup. Another Bertolli soup made this short list, a Spinach Soup from his Chez Panisse Cooking  with Alice Waters.
With autumn here—perhaps the best growing season for spinach, along with spring—it seems like the perfect time to finally enjoy this extraordinary soup. Bertolli writes “[t]his is one of the simplest and most economical soups I know of, and it takes very little time to make.” If you are quick with a knife, this soup goes from cutting board to table in 30 minutes. And nothing is lost to speed. To my taste, Bertolli’s Spinach Soup ranks as one of the most delicious soups in my entire cookbook collection. As a starter, Bertolli’s recipe serves 8.
4 tablespoons unsalted butter
5¼ cups water
1 large carrot (4 ounces), diced
1 stalk of celery (2½ ounces), diced
1 medium yellow onion (6 ounces), diced
3 bunches of spinach (1 pound, 2 ounces), de-stemmed, washed and drained
Salt and pepper
Melt the butter in a wide stainless-steel pot (at least 5-quart capacity). Add ¾ cup water and the carrot, celery, and onion. Cook at a low simmer, covered, for 20 minutes.
Add the remaining 4½ cups water and bring to a boil. Add the spinach and cook over high heat for 1 minute, stirring until all of the spinach is well wilted. Do not cover the pot: volatile acids, which are released when the vegetable is heated, will condense on the lid, fall back into the pot, and cause discoloration. Purée the entire mixture thoroughly in a blender, do not sieve, and transfer the soup immediately to a hot tureen. Season with salt and pepper to taste, garnish as desired, and serve immediately.
As to garnishes, Bertolli suggests a few options in his introduction to the recipe. Consider adding garlic butter or crème fraîche thinned to the soup’s consistency. Better yet, he writes, serve with “grated Parmesan, small buttered garlic croutons, and extra virgin olive oil drizzled over the surface.” Personally, I think this is all gild for the lily; I serve the soup without any embellishment.
A word or two on selecting and cleaning spinach: look for perky, fresh leaves with an intense green color. A good bunch will squeak when squeezed. Bertolli prefers a smooth-leaf spinach over the heavy, crinkle-leaf varieties, such as Bloomsdale, but writes that either type works well in this soup.
Take care washing fresh spinach, which often harbors sand and dirt. After stemming, place the leaves in a very large bowl filled with cold water and mix the spinach around with your hand. Wait a minute for any sand and dirt to drift away to the bowl’s bottom. Then gently lift out the spinach so as not to disturb the settled grit. I typically repeat this process a couple more times especially if the spinach seems particularly dirty.