Place the 2 cups of dry pinto beans, 6 cups of water, and 1 cup of vegetable broth into a pot and bring to a boil. Then, turn the heat down to a simmer and cook for 10 minutes while stirring occasionally. Then, let it stand for 60 minutes without heat.
Chop the 1 cup of tomatoes, 2 cloves of garlic, 1 whole serrano pepper, and 1 cup of yellow onion to their respective sizes.
In a slow cooker, add the pinto beans, tomatoes, onion, 1 tsp of cumin, serrano pepper, and garlic. Cook on a high heat for 5 hours or until the pinto beans are tender.
Peel and slice the 1 whole avocado in half and remove the seed. Then, slice each half into thin strips and use as a topping for serving the soup. Enjoy!