Place the dried mushrooms in a small pot with the stock over medium heat. Let simmer for 15-20 minutes until softened. Remove the mushrooms from the stock to cool, then chop.

Meanwhile, roughly chop the fresh mushrooms and add to a large soup pot over medium-high heat with a drizzle of olive oil and the crushed red pepper. Cook for 10 minutes, stirring, until the mushrooms are wilted and dark in color. Add the onion and garlic, and cook for 5 more minutes. Pour in the beef stock used for the dried mushrooms, the Worcestershire sauce, and ⅔ of the reconstituted chopped mushrooms.

Puree the soup in a blender, food processor, or with an immersion blender. Add the half and half and taste the soup; add salt or more crushed red pepper to your taste. If the soup seems thick, add water ¼ cup at a time to reach a consistency you like.

Serve the soup topped with the remaining reconstituted mushrooms and green onions, if desired.