Sauté onion and garlic in a pot with a little broth until softened.

Add broccoli and spinach to the pot. Pour in the remaining vegetable broth.

Bring to a boil, then reduce heat and simmer for 20-25 minutes, or until vegetables are tender.

Carefully blend the soup until smooth using an immersion blender or a regular blender (in batches).

Stir in butter (optional).

To make the eyeballs, carefully create a small indentation in each mozzarella pearl and insert a slice of black olive.

Ladle soup into bowls and top with desired number of eyeballs.