Preheat the oven broiler on low.
Heat a pot on medium heat. Once hot, add the oil, onion, celery, and garlic. Cook until softened, then stir in the cardamom.
Add the chicken broth and cauliflower. Season with salt and pepper. Simmer with a lid for 25 minutes.
In the meantime, mix the cut up bread with 1 to 2 teaspoons of oil, garlic powder, and season with salt and pepper. Place under the broiler until golden brown and hard like croutons. Then set aside.
Using a blender or immersion blender, blend the soup until smooth. Return to the pot and stir in the scallions. Taste and adjust the seasoning with salt and pepper.
Top the soup with croutons, scallions, and drizzle with olive oil.