Heat the oil in a large heavy-duty pot over medium high heat. Add the onion, carrots, celery, and mushrooms. Season with salt and pepper and cook until soft and translucent, 3 to 5 minutes. Add the garlic and cook until fragrant, 45 to 60 seconds, Add the bay leaves, thyme, vegetable juice, tomatoes, and miso paste. Stir to combine. Add the butterbeans and sweet potatoes. Bring to a boil over high heat. Reduce the heat to simmer. Cook until the vegetables are just tender, about 15 minutes. Add the okra; cook until tender, about 5 minutes. Add red pepper flakes; stir to combine. Taste and adjust for seasoning with salt and pepper. Ladle into warm bowls and serve immediately.