Step 1: Prepare your ingredients. Clean and slice mushrooms, finely dice the onion, and mince the garlic. Measure out your broth, flour (or GF blend), and cream (or dairy-free alternative).
Step 2: In a large heavy-bottomed pot or Dutch oven, heat olive oil and butter (or just olive oil for dairy-free) over medium heat. Add the diced onion and cook until softened and translucent, about 5-7 minutes.
Step 3: Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Step 4: Add the sliced mushrooms to the pot. Cook, stirring occasionally, until the mushrooms release their liquid and begin to brown, about 8-10 minutes. This caramelization adds deep umami flavor.
Step 5: Sprinkle the all-purpose flour (or gluten-free flour blend) over the mushrooms and onions. Stir well to coat everything, cooking for 2 minutes to cook out the raw flour taste and form a roux.
Step 6: Gradually pour in the vegetable broth, a cup at a time, whisking constantly to prevent lumps. Add the dried thyme. Bring the soup to a gentle simmer and let it cook for 10-15 minutes, stirring occasionally, until it thickens.
Step 7: Reduce the heat to low. Stir in the heavy cream (or coconut/cashew cream). Do not let the soup boil after adding the cream.
Step 8: Season the soup generously with salt and freshly ground black pepper to taste. Adjust as needed. For an extra boost of flavor, add a squeeze of lemon juice.
Step 9: For a smooth soup, use an immersion blender to blend directly in the pot until desired consistency is reached. For a chunkier soup, blend only half, or skip blending entirely.
Step 10: Ladle into bowls and garnish with fresh chopped parsley before serving.