Heat the coconut oil in a Dutch oven set over medium heat. Add the leeks, carrots and celery, and saute until soft, about 5 minutes. Add the mushrooms, garlic, thyme, bay leaves and creole seasoning; stir, and saute 2 more minutes.
Add the mushroom broth, beer, tomatoes and pinto beans. Bring to a simmer, then cover with a tight-fitting lid and cook until the beans are tender, about 1 hour.
Uncover the pot and cook until the liquid is reduced by one-third, about 15 minutes. Season with 2 tablespoons of the miso paste and some pepper. Taste and add more miso as needed.