Put onions and jalapenos in food processor and puree. Place the onion, rinsed beans, jalapeno, garlic, pepper, and cumin into a slow cooker. Pour in the chicken broth and stir all ingredients to combine. Cook on high in a 6 or 6 1/2 quart slow cooker for 8 hours, adding water if needed.
Once the beans have cooked, strain them reserving the liquid. Mash the beans with a potato masher, adding the reserved broth as needed to attain desired consistency.