Creamy Broccoli Soup With Broccoli Rabe

8 ounces plain nonfat yogurt
2 teaspoons unsalted butter
1 medium onion, peeled and chopped
1 bunch broccoli (about 1 1/2 pounds), trimmed, stalks peeled and cut into 1/2-inch rounds
3 ½ cups chicken broth, homemade or low-sodium canned
2 teaspoons salt
Freshly ground pepper to taste
Small pinch cayenne
4 stalks broccoli rabe, ends trimmed off

Nutritional Information
- Nutritional analysis per serving (4 servings)
  192 calories; 5 grams fat; 2 grams saturated fat; 0 grams trans fat; 1 gram monounsaturated fat; 0 grams polyunsaturated fat; 20 grams carbohydrates; 5 grams dietary fiber; 9 grams sugars; 18 grams protein; 8 milligrams cholesterol; 2639 milligrams sodium

Four servings

Place the yogurt in a sieve lined with a paper towel. Set aside until all of the liquid has drained off, several hours or overnight in the refrigerator.
Melt the butter in a large pot over medium heat. Add the onion and cook until soft, about 5 minutes. Add the broccoli stalks and florets and 3 cups of the chicken broth and bring to a boil. Reduce to a simmer, cover and cook until the broccoli is soft, about 20 minutes.
Place half of the broccoli and cooking liquid with half of the yogurt in a blender. Hold the top down firmly with a kitchen towel and blend until coarsely pureed. Scrape the mixture into a large saucepan and repeat with the remaining broccoli, cooking liquid and yogurt. Stir in the remaining 1/2 cup chicken broth, the salt, pepper and cayenne. Warm the soup over low heat.
Separate the broccoli rabe stems from the leaves. Cut the stems into 1/2-inch pieces and cut the leaves across into thin strips. Bring a medium-size pot of lightly salted water to a boil. Add the stems and blanch for 2 minutes. Remove with a slotted spoon. Add the leaves and blanch for 1 minute. Drain. Divide the soup among 4 bowls. Top with the broccoli rabe stems and then the leaves and serve immediately.