2 Servings; Can be doubled.
1 teaspoon dried rosemary
Melt butter in heavy large saucepan over medium-low heat. Add leeks; cover and cook until just softened, about 5 minutes. Add 3 cups broth, cooked or frozen vegetables, potato, cabbage and rosemary. Bring soup to boil. Reduce heat; partially cover pan and simmer until all vegetables are tender, about 15 minutes. Thin soup, if desired, with additional broth. Season with salt and pepper. Ladle soup into bowls. Sprinkle croutons over.