From Bon Appétit, February 2011
3 tablespoons butter
3 cups chopped leeks (white and pale green parts only; about 3 large)
6 teaspoons chopped fresh thyme, divided
1 1/4 pounds broccoli crowns, chopped (about 8 generous cups)
4 cups (or more) low-salt chicken broth
Melt butter in large pot over medium-high heat. Add leeks and 4 teaspoons thyme; sauté until leeks are almost soft, reducing heat if needed to prevent rapid browning, 7 to 8 minutes. Transfer 1/2 cup leeks to small bowl; reserve. Add broccoli and 4 cups broth to pot; bring to boil. Cover; boil until vegetables are tender, 8 to 10 minutes.
Puree soup in blender until smooth. thin soup with more broth, if desired. Season with salt and pepper. Ladle into bowls; sprinkle with 2 teaspoons chopped thyme and reserved leeks.