In a large pot, melt butter over medium heat. Add chopped onion and cook until translucent, about 5 minutes.
Add minced garlic and cook for another minute until fragrant.
Add broccoli florets and cook for 3-4 minutes.
Pour in vegetable broth, season with salt and pepper, and bring to a boil. Reduce heat and simmer until broccoli is tender, about 15 minutes.
Use an immersion blender to puree the soup until smooth, or carefully transfer to a blender in batches and blend until smooth.
Return the soup to the stove, stir in heavy cream, shredded cheddar, and Parmesan cheese. Heat gently until cheeses are melted and soup is heated through.
Taste and adjust seasoning if necessary. Serve hot, garnished with additional cheese if desired.
Notes
A simple, hearty soup with fresh ingredients, perfect for a cozy dinner.