Brown the Mushrooms for Maximum Flavor
Heat the olive oil and butter in a large pot or Dutch oven over medium-high heat. Add the mushrooms in a single layer, working in batches if necessary to avoid overcrowding the pan. Cook without stirring for a few minutes, then toss and continue cooking until they are deeply browned and caramelized, about 8-10 minutes per batch. This step is crucial for developing a rich, savory flavor.

Sauté the Aromatics Until Soft
Remove the browned mushrooms from the pot and set them aside. Add the chopped onion, salt, and a few grinds of black pepper to the pot. Cook, stirring occasionally, until the onion has softened and is translucent, about 5-7 minutes. Stir in the grated garlic and cook for one more minute until fragrant.

Deglaze and Combine
Pour in the dry white wine to deglaze the pot, using a wooden spoon to scrape up any flavorful browned bits from the bottom. Allow the wine to bubble and reduce by about half. Return the cooked mushrooms to the pot and stir to combine.

Simmer the Broth to Meld the Flavors
Add the vegetable broth, tamari, and fresh thyme leaves. Bring the mixture to a boil, then reduce the heat to low, partially cover the pot, and let it simmer gently for 15-20 minutes. This allows all the flavors to meld together beautifully.

Blend to Your Desired Consistency
For a rustic, slightly chunky soup, use an immersion blender to pulse the soup directly in the pot until it reaches your desired texture. For an ultra-smooth and velvety consistency, carefully transfer the soup in batches to a stand blender and blend until completely smooth.

Finish with Cream and Final Seasoning
Return the blended soup to the pot over low heat. Stir in the heavy cream (if using) and warm it through gently, being careful not to let it boil. Taste the soup and adjust the seasoning with more salt and pepper if needed. Serve hot, garnished with fresh thyme, parsley, and a drizzle of olive oil.