Preheat your oven to 400°F (200°C). Slice the tops off the heads of garlic, drizzle them with olive oil, and wrap them tightly in foil. Place in the oven and roast for about 30 minutes.

In a large pot, heat olive oil over medium heat. Add chopped yellow onions and sauté for 5-7 minutes until translucent and soft.

Squeeze the roasted garlic into the pot, add broth and fresh thyme, stirring well. Bring to a gentle simmer.

Reduce heat to low and let simmer for 15-20 minutes, stirring occasionally to ensure nothing sticks.

Remove thyme sprigs and blend the soup until smooth and creamy using an immersion blender.

Return the pureed soup to low heat and stir in heavy cream, seasoning with salt and black pepper. Warm through.

Ladle the soup into warm bowls and garnish with fresh herbs or croutons, serving alongside crusty bread.