In a medium-sized pot over medium heat, melt butter and sauté onion and garlic until barely translucent, about 5 minutes. Add sunchokes and vegetable stock. Let simmer about 30–40 minutes or until sunchokes are soft when you poke them with a fork. Blend together with an immersion blender until smooth. Make sure that the texture isn’t too liquidy. If unsure if it is too liquidy, set aside some of the stock before blending, which can be added later. Add salt and pepper to taste and serve immediately.
Heat olive oil in a large stock pot. Sauté onion until translucent; add other vegetables, and sauté until they are sweating and cooked, 8–10 minutes. Add water and bring to a boil. Add salt and pepper and cook on medium heat for another 5–10 minutes, until broth has taken on the flavor of the vegetables. Strain and set liquid aside to use in soup.