Heat oil in a cast iron pot and cook chopped onion with cumin, paprika and oregano over low heat for 10 minutes until tender. Add sliced garlic and minced chilli, cook while stirring for 2 minutes longer.
Then add beef and pork and brown for 5 minutes, add bay leaves, chipotle paste, chopped tomatoes, 1 tsp of salt. Turn the heat up and bring to a boil.
As soon as it boils, turn the heat to medium-low, add chocolate squares, allow it to melt for a minutes or two and then stir, cover with a lid and let it simmer for 1 1/2 hours. Check on it occasionally and stir to prevent from burning.
After 1 1/2 hours your meat should be very tender. At this point take a potato masher to the chilli and smash the pork loin chunks slightly while still leaving some texture.
Add beans and corn, taste and adjust seasoning if needed.
Continue cooking for another hour on low heat.
Serve with a dollop of plain yogurt and fresh chopped cilantro alongside rice or tortillas.