Cut the top 1⁄4 inch off the bulb of garlic, exposing the cloves. Place on a sheet of aluminum foil that is large enough to wrap around the entire bulb. Drizzle the bulb of garlic with the olive oil, then sprinkle with salt and pepper. Bake for 30 minutes or until the garlic is fragrant and the cloves are tender and caramelized.
Heat the butter in a stock pot or dutch oven over medium-low heat. Add the onion and celery and sauté for 5 minutes, or until soft.
Add the mushrooms, parsley, thyme, salt and pepper to the pot, and sauté for an additional 5 minutes, or until the mushrooms have released their liquid and are tender. Spoon out a couple tablespoons of the vegetables to use as a garnish.
Add the chicken stock, cream, and 6 cloves of roasted garlic to the pot. Bring to a boil over medium-high heat, then reduce to low to simmer. Let the soup simmer for about 30 minutes, stirring occasionally.
Transfer to a high-powered blender (alternatively, you could also use an immersion blender right in the stock pot). Pulse until smooth, being careful not to overfill the blender cup as hot liquids will rise in volume. If necessary, do this in two batches.
Pour the soup back into the stock pot, taste, and add more salt and pepper, if desired.
Top with chopped bacon, reserved vegetables, remaining roasted garlic cloves, parsley, and a swirl of olive oil.