Quick Curried Cauliflower Soup

Name: Quick Curried Cauliflower Soup
Yield: 8 to 10 Servings
Ingredients: 2 tablespoons olive oil; 1 large onion, chopped; 1 1/2 tablespoons sugar; 4 teaspoons curry powder; 8 cups cauliflower florets (from 1 large head), chopped; 10 ounces Yukon Gold potatoes, peeled, diced into 1/2-inch cubes (about 1 1/4 cups); 7 cups low-salt chicken broth; Plain yogurt; Chopped fresh mint