Preheat oven to 350 degrees and grease a small baking dish. Place chicken in greased baking dish, brush with oil, and sprinkle with salt and pepper. Bake for 30 min. Once finished baking, take two forks and shred chicken.
While chicken is baking, take a large pot and sauté garlic, onion, and spices in oil over medium heat for approximately 5 min.
Add tomatillos, celery, leeks and sauté for 10 min.
Stir in broth, navy beans, salsa verde, and pulled chicken. Bring to a boil and then simmer for 20 min.
Before serving, mix in lime juice. Garnish with cilantro and avocado before serving.