Use any beans that sound good to you! I prefer to have either corn in my chili or tortilla chips as a garnish, not both at the same time, but once again do what sounds good to you. If you like your chili spicy, use more chipotle chile peppers or add some cayenne.
Heat a large pot or Dutch oven over medium high heat. When hot, add the oil and when it shimmers add the onions with a pinch of salt.
Cook the onions for 7-8 minutes, until they are becoming translucent. Add the garlic and the canned diced green chile peppers. Stir and cook for another 2-3 minutes.
Add the chopped sweet bell pepper with another pinch of salt. Stir and let cook for 5 minutes, stirring occasionally. If the vegetables have stuck or scorched at all, add a small splash of cider vinegar.
Add the ground beef. Break it up into clumps and sprinkle with a pinch of salt. Mix into the onions. Let the beef brown, stirring occasionally, about 8-10 minutes.
Add the chile powders, cumin and cinnamon. Stir into the ground beef mixture and let the spices roast. Add the minced canned chipotle pepper. Stir it into the mixture and let everything cook for 3-5 minutes. If anything is scorching or sticking, add a small splash of cider vinegar.
Add the fire roasted tomatoes. Mix into the ground beef mixture until incorporated. Stir in the cocoa powder. Let simmer for 5 minutes.
Add the rinsed and drained beans with 1 cup of chicken stock. Stir and bring to a simmer. Let simmer, partially covered, for 30 minutes.
A good chili should be rich and stew-like, but not watery or brothy. If the chili is getting too dry after 30 minutes add more chicken stock. At the 30 minute mark is also when you add the corn if using. If you need to add more stock, let it simmer for 10-15 minutes after adding in order to blend the chicken stock into the chili; if you only added corn, 5-7 minutes should do. Turn the heat down to a lower simmer if it is evaporating too quickly.
Stir the 1 tablespoon of cider vinegar into the chili. Stir and taste for more vinegar and more salt.
Serve with cilantro, shredded cheeses and sour cream, and tortilla chips if desired.