Take whole cremini mushrooms, slice in half. Add ½ of the pre-sliced white mushrooms to the pile. Reserve the rest of the pre-sliced white mushrooms for the topping.
Cut the end off of the fennel, slice the bulb into thin pieces and discard the rest. Chop shallots and garlic, and tear leaves from two sprigs of marjoram.
Get out a large pot or dutch oven. Pour 1 glug olive oil into the pot and add the garlic, fennel, shallots and marjoram. Sprinkle liberally with kosher salt and cracked pepper. Sauté 5-10 minutes.
Add the mushrooms, sauté a few more minutes. Add sherry and let simmer for another few minutes.
Season again with kosher salt and cracked pepper, and add vegetable broth. Cover and let simmer for about 45 minutes to 1 hour.
While the soup is simmering, place whole shitakes and remaining sliced mushrooms on a parchment-lined baking sheet. Sprinkle with kosher salt and remaining marjoram leaves. Add 1 glug olive oil, toss the mushrooms to coat. Bake until the mushrooms are cooked through, about 30 minutes.
Check your soup. When the mushrooms are soft and the broth is a rich brown, it’s ready. Turn off the heat.
Get out your immersion blender (or regular blender). Blend soup to your desired consistency. I wanted mine pretty smooth, but not without texture. Add heavy cream and stir. Season as needed.
To serve, top soup with roasted mushrooms, a dash of olive oil and some leftover fresh marjoram leaves, if desired.