Preheat the oven to 400°F (205°C).
Cut the top part off the bulb of garlic. Place on a piece of baking paper, drizzle generously with the olive oil, and season with salt and pepper. Roast in the preheated oven for 30 minutes until soft and golden brown.
Heat the butter in a saucepan and sauté the onion with the celery for 3-5 minutes until fragrant.
Toss in the mushrooms, parsley, and thyme, season with salt and pepper, and cook for 5 more minutes. Reserve 2-3 tablespoons of that mix to garnish the soup.
Pour the chicken stock, cream, and half the roasted garlic cloves into the pot.
Bring to a boil and then reduce to a gentle simmer for about 20 minutes.
Transfer to a food processor or use a stick blender to process the soup until smooth and creamy.
Serve the soup hot, topped with chopped crisped bacon, reserved vegetables, roasted garlic cloves, parsley, and a big swirl of olive oil.