Soup:
Peel and roughly chop the Jerusalem artichokes and potatoes.
Peel and chop the onions and garlic.
Heat a pot with butter and oil, then sauté the onions, garlic, Jerusalem artichokes, and potatoes for 2-3 minutes. They should not brown. Add thyme.
Add the stock and let the soup simmer for about 20 minutes, or until everything is tender.
Remove the soup from the heat and blend it with an immersion blender.
Add cream and heat the soup to boiling point.
Season the soup with salt, pepper, and grated nutmeg.
Butter-Fried Mushrooms:
Start by cleaning the mushrooms.
Firm mushrooms such as button mushrooms can be briefly rinsed under cold water, and the stems trimmed.
Softer and more irregularly shaped mushrooms like oyster mushrooms and chanterelles should not be rinsed but rather brushed free of soil and debris.
Cut the mushrooms into smaller pieces and fry them crispy in butter in a pan. Season with salt and pepper.
Serve the Jerusalem artichoke soup with the butter-fried mushrooms.
