In a large heavy soup pot, heat butter and olive oil over medium heat until the butter melts. Add scallions and cook for 2-3 min, then add the carrots and garlic. Cook until soft, about 5 min.
Add the beans and stock and bring to a boil. Add the bay leaves and tarragon leaves, simmer, and cook 15-20 min until the beans are falling apart. Blend with a hand-held blender or blender to desired consistency.
Taste for seasoning and adjust as needed. Serve with a drizzle of olive oil, and fresh black pepper.
* To make vegan, replace the butter with vegan butter or oil.
