First, in a 6 qt or larger slow cooker, add oil and onions (because this allows the onions to season the oil) followed by ground beef and chorizo. Break apart the meat.
Next, add the beans, tomatoes with juice, tomato paste and spices.
Then, cover slow cooker, set on low setting and cook for 4 hours. Stir well midway through and at the end of cooking.
Notes
Storage
Store leftovers in the refrigerator for up to three days for maximum flavor. Put in containers and freeze for up to 6 months for best flavor.