Combine the soup seasonings and set aside (do not include the salt). Measure out remaining ingredients before beginning.
Take ¾ of the mushrooms and roughly dice them. Keep the remaining slices whole.
Heat olive oil in a soup pot over medium-high heat. Add the mushrooms and sprinkle with salt. Sauté for 10 minutes until softened, stirring frequently. When you begin to see water in the pot, increase the heat slightly and stir continuously to allow the water to evaporate. Remove the mushrooms and set aside.
Reduce heat to medium. Add the butter and diced onions. Let the onions soften for 15 minutes, stirring frequently, until they start to caramelize slightly. This will add depth of flavor to the soup.
Add the wine, garlic, Worcestershire sauce, mustard, and soup seasonings. Reduce the wine by half, about 5-6 minutes. Stir in the flour and cook for 2 minutes, stirring continuously.
Add the chicken broth in small splashes, stirring continuously. Add the heavy cream in the same manner, followed by the bouillon cube. Bring to a boil, then reduce to a simmer.
Add up to 1 ½ cups of diced mushrooms to the soup and use an immersion blender to blend the mushrooms and onions into the broth until smooth. (You can also transfer to a blender in batches.) Add the remaining sliced/diced mushrooms so that there is some texture to the soup.
Simmer uncovered for 10-15 minutes, or until desired thickness is obtained. The longer the soup simmers, the thicker and more concentrated it will become.
Taste and season with salt/pepper if desired. Serve!
Notes
Pro Tips:
Mushrooms: I recommend using Cremini (Baby Bella) mushrooms for this recipe, but white button mushrooms may also be used. Cremini mushrooms are at a later stage of growth and therefore have a deeper, earthier flavor. They're also darker in color. I choose ones that are already washed/sliced to save time!
Garlic:Use fresh garlic cloves for this recipe (not jarred minced garlic), the taste is so much better. Shallots are also great, or a combination of both!
Wine: Pinot Grigio, Chardonnay, or Sauvignon Blanc are perfect dry white wines for this recipe. Chicken broth may be used if you don’t cook with wine.
Chicken Broth and a Beef Bouillon cubeis used in this recipe for a delicious flavor contrast, it makes a big difference to incorporate both.
Vegetarian Version:Vegetarian chicken broth and beef bouillon can be used if needed, Better Than Bouillon makes chicken and beef varieties that are vegetarian.