Sauté Aromatics: Heat olive oil in a large saucepan over medium heat. Add chopped onion and sauté for 3–4 minutes until soft and translucent. Add garlic and cook for 30 seconds until fragrant.

Cook Zucchini: Add chopped zucchini to the pan and cook for 3–4 minutes, stirring occasionally.

Add Broth and Simmer: Pour in vegetable broth and bring to a boil. Reduce heat and simmer for 10–12 minutes until zucchini is tender.

Blend the Soup: Remove from heat and add fresh basil leaves. Blend using an immersion blender or transfer to a countertop blender until smooth.

Finish with Parmesan: Stir in grated Parmesan cheese. Season with salt, black pepper, and nutmeg (if using). Adjust thickness with extra broth if necessary.

Serve: Serve hot, garnished with extra Parmesan, basil leaves, croutons, or a drizzle of olive oil or cream.