Heat the olive oil in a large soup pot. Sauté the chopped onions and leeks until softened (~3-5 minutes).
2 tablespoon olive oil , 2 yellow onions, 2 leeks (only white part)
Add the mushrooms, minced garlic, salt and pepper and cook until they release their moisture and become golden brown (5 minutes). Stir constantly to avoid burning.
3 garlic cloves, 8 oz brown mushrooms, 1 teaspoon salt, pinch of black pepper
Add the diced potatoes, broth and white wine (if using) and all the fresh herbs. Bring the mixture to a simmer and let it cook covered with a lid for about 15-20 minutes or until the potatoes are tender.
3 cups peeled and cubed potatoes , 5 cups broth, ½ cup dry white wine (optional), 1 sprig of fresh thyme, 1 sprig of fresh parsley, 1 sprig of fresh marjaram, 1 sprig of fresh lemonbalm
Remove the herbs from the soup. Stir in the grated Parmesan and heavy cream (if using), allowing it to melt into the soup.
Taste and adjust the seasoning. You might need to add some more salt. The amount of salt needed also depends on how salted your broth is.
Allow the soup to cool until it's cold enough to handle. Using a stick blender or a regular blender, blend the soup until you achieve your desired consistency. If using a regular blender, work in batches and be cautious with hot liquids. You can either blend the entire soup or reserve a portion of the soup for a chunkier texture. Serve the soup hot (you might need to reheat it), garnished with additional Parmesan, a drizzle of olive oil and fresh herbs.