In a large pot or Dutch oven, heat the olive oil and butter over medium heat. Once the butter is melted and bubbling, add the chopped sweet onion. Sauté for about 5 minutes, or until the onion becomes translucent and fragrant.
Next, add the sliced button mushrooms to the pot. Cook for another 8-10 minutes, stirring occasionally until the mushrooms release their moisture and start to brown.
Stir in the minced garlic, chopped fresh thyme, and the bay leaf. Cook for an additional 2 minutes, allowing the flavors to meld together beautifully.
Add the chicken broth to the pot, scraping the bottom to release any flavorful bits stuck to the bottom. Bring the mixture to a gentle simmer and let it cook for about 15 minutes, allowing the flavors to deepen.
Remove the bay leaf and use an immersion blender to puree the soup until smooth. If you prefer a chunkier texture, blend just half of the soup and leave the rest as is for added texture.
Stir in the half and half and Worcestershire sauce. Continue to simmer for another 5 minutes, tasting and adjusting the seasoning as needed. A sprinkle of salt and pepper may be just what it needs!
Ladle the Cream of Mushroom Soup into bowls and garnish with a drizzle of olive oil or a sprinkle of fresh thyme. Serve it warm with crusty bread for a comforting meal.
