Preheat oven to 400 degrees F. Line a baking sheet with parchment paper.

Place mushrooms in a single layer onto the prepared baking sheet. Add olive oil, half of the garlic and 4 sprigs thyme; season with salt and pepper, to taste. Gently toss to combine.

Place into oven and bake for 20-30 minutes, or until browned and tender, stirring once. Let cool before coarsely chopping; set aside.

Melt butter in a large stockpot or Dutch oven over medium heat. Add onion, and cook, stirring constantly, until golden and caramelized, about 10-15 minutes. Stir in remaining garlic until fragrant, about 1 minute.

Whisk in flour until lightly browned, about 1 minute. Stir in wine, scraping any browned bits from the bottom of the pot.

Stir in chicken stock, bay leaves and remaining thyme; season with salt and pepper, to taste. Bring to a boil; reduce heat and simmer until slightly reduced, about 15 minutes.

Stir in mushrooms; simmer until thickened, about 10-15 additional minutes. Remove from heat; stir in heavy cream.

Serve immediately.