
In a large stockpot, melt the butter over medium heat. Stir in the onions, celery and garlic. Cook for 7-8 minutes, until soft.
Stir in the salt and pepper and dried thyme. Whisk for 3 minutes and then stir in the broth. Slowly mix in the broccoli florets. Bring to a simmer and then reduce heat to medium low.
Cover and cook for 40 minutes, until the broccoli is soft.
Stir in the heavy cream and cream cheese, stirring constantly over medium-low heat. Once the cheese is melted, simmer on low for another ten minutes.
Remove from heat and use an immersion blender to blend the soup until smooth and creamy. Serve immediately. Add cheddar cheese and croutons on top, if desired as a garnish.
This soup can be reheated and will last in the refrigerator for up to 4 days.