Step 1

Melt the butter and olive oil in a 5-qt. or larger stockpot over medium-high heat. Add the onion and cook until it’s beginning to brown (resist the urge to stir too often), about 4 minutes. Stir in the garlic and cook for 1 minute. Add the mushrooms, 2 Tbs. of the thyme, and 1/2 tsp. each salt and pepper; cook until the mushrooms become limp, 2 to 4 minutes.

Step 2

Add the broth, scraping up any browned bits in the pot with a wooden spoon. Bring to a boil over high heat, reduce the heat to maintain a simmer, and cook until the mushrooms are tender, 7 to 10 minutes. Remove from the heat and let cool slightly. Transfer about half of the soup to a stand blender and process until smooth. Return the mixture to the pot and stir in the half-and-half, sherry, and soy sauce. Add more salt and pepper to taste, if needed, and reheat. Garnish each serving with a small pinch of the remaining 1 tsp. thyme.