Heat olive oil in a large pot over medium heat.
Add chopped onion and sauté until translucent.
Stir in minced garlic and cook for an additional minute.
Add broccoli florets and sauté for 3-4 minutes.
Pour in vegetable broth and bring to a boil.
Reduce heat and let simmer for 15 minutes, until broccoli is tender.
Use an immersion blender to puree the soup until smooth.
Stir in heavy cream and shredded cheddar cheese.
Season with salt and pepper to taste.
Serve hot, garnished with croutons if desired.