Jerusalem artichokes, also called sunchokes, are neither native to Jerusalem nor a type of artichoke. Oddly enough, they’re actually a North American vegetable that vaguely resembles ginger root, with a slightly nutty flavor. They’re delicious roasted, and are a wonderful addition to this soup, lending it a creamy texture and amazing flavor.
Heat the olive oil in a 6-quart soup pot over a medium flame. Add the onions and sauté until translucent.
Add the garlic and cook for 1 to 2 minutes, until golden (making sure it doesn’t burn). Add the potatoes, Jerusalem artichokes, and broth and stir well.
Season with fennel seeds, salt, and pepper. Bring to a boil and cook for 10 minutes.
Reduce heat to low, cover, and simmer for another 20 to 25 minutes. Remove from heat.
Using an immersion blender, purée the soup. Return to a low heat and cook for another 5 to 10 minutes.