3 to 4cupslow sodium vegetable broth or chicken broth
1(12-ounce can) low fat evaporated milk
1/2cupplain full-fat Greek yogurt(do not use low fat or fat free or it may curdle)
Chopped fresh parsley(do not skip)
Freshly ground black pepperfor serving
Toasted baguette slicesoptional for serving
In a Dutch oven or similar large, sturdy pot, heat 1 tablespoon of the olive oil over medium. Add about 1/4 of the mushrooms and 1/4 teaspoon salt. Sauté until the mushrooms are nicely browned, about 8 minutes. Remove to a plate.
In the same pot, heat the butter and remaining 1 tablespoon olive oil over medium. Once the butter has melted, add the remaining mushrooms, onion, thyme, black pepper, and remaining 1 teaspoon salt. Sauté until the onion is very soft and the mushrooms have browned, given up their liquid, and most of the liquid has cooked away, about 10 to 12 minutes. Don’t shortcut this step, as it's key to building flavor.
Stir in the garlic and cook 30 seconds.
Sprinkle the flour over the top and stir to combine. Continue to cook and stir for 2 full minutes so that the flour is completely cooked.
Slowly pour in the wine, stirring as you go. Let simmer for 2 minutes, stirring constantly and scraping along the bottom. The mushrooms will be thick, soft, and deeply colored.
Slowly pour in 3 cups of the broth and evaporated milk, stirring constantly. Keep on stirring to minimize lumps.
Increase the heat to medium high and bring the mushroom soup to a gentle boil. Continue cooking and maintaining that gentle boil, stirring and scraping along the bottom periodically, for 10 minutes until the soup has thickened.
With an immersion blender puree the soup until the mushrooms are in small bits. (You can also carefully transfer the soup to a blender to puree. Be VERY careful not to overfill your blender as hot soup splatters; do not fill the blender more than halfway to the top.)
Transfer the soup back to the pot if needed. Stir in the Greek yogurt, balsamic vinegar, and soy sauce. If the mushroom soup is thicker than you would like, add additional broth to reach your desired consistency. Taste and adjust the seasoning to your liking. Serve warm topped with the reserved mushroom slices, a few twists of freshly ground pepper, and a generous sprinkle of parsley.
TO STORE: Refrigerate soup in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a Dutch oven on the stovetop over medium-low heat or in the microwave.
TO FREEZE: Freeze soup in an airtight, freezer-safe storage container for up to 3 months. Let thaw overnight in the refrigerator before reheating.