Sweet and sour butternut squash soup

Ingredients:

• 1 medium butternut squash (about 1 kg), peeled, seeded and diced
• 3 tbsp. l. olive oil
• 1 onion, thinly sliced
• 4 cloves garlic, crushed
• 2 fresh sage leaves
• 2 teaspoons coarse salt
• 2 medium canned plum tomatoes
• 4 cups lightly salted chicken broth or water
• 1 teaspoon balsamic vinegar
• 2 tbsp grated Parmesan (optional)

Preparation:

1. Heat olive oil in a saucepan over medium heat. Add the onion, garlic, sage, 1 teaspoon of salt, and season with pepper to taste. Cook, covered, stirring occasionally, until softened and fragrant, about 15 minutes.
2. Increase the heat to medium-high, add the tomatoes, and cook, stirring with a wooden spoon, until the tomatoes break down and the onions are lightly browned, about 7 minutes. Add the squash and the remaining 1 teaspoon of salt and continue cooking, stirring occasionally, until the squash is tender, about 12 minutes. Then pour in the broth, bring to a simmer, and simmer until the vegetables are tender, about 20 minutes. Let the soup cool slightly.
3. Next, puree the soup in batches in a blender or with an immersion blender. Pour the soup back into the saucepan and heat over medium heat. Stir in the vinegar. Serve the soup in warm bowls, sprinkled with Parmesan cheese if desired.