Season the brisket generously on all sides with salt and pepper. Next, add the olive oil to a very large sauté pan on high heat and brown the brisket on all sides.
Once the brisket is caramelized, add it to a slow cooker along with stout beer, can of chopped tomatoes and salt and pepper, and cook on high heat for 8 hours.
After the brisket has cooked for 4 hours, add 1 tablespoon of olive oil to a very large pot on medium-high heat. Next, add in the onions and garlic and caramelize. Once the onions and garlic are brown, add in the peppers and cook for 10 minutes on high heat.
Add in the beans, tomatoes, and seasonings (except the chocolate) and stew on low heat until the brisket is finished cooking.
Once the brisket is done, pull it apart using two forks so that it is completely shredded. Add the entire pot of brisket including the beer and tomatoes to the pot of chili.
Thicken with tomato paste if need be. Finish by stirring in chocolate and seasoning with salt and pepper.