Heat olive oil in dutch oven or large pot over medium high heat until shimmering. Add onion and bell pepper and saute until onion is soft and translucent, about 6-8 minutes. 

Add the garlic and cook a few minutes more until fragrant then add in chili powder, cumin, oregano, salt, and a bit of fresh black pepper and stir for 1 minute more. 

Add in the tomatoes, chicken broth, pinto beans, chocolate, cinnamon, tomato paste, and red pepper flakes and bring to a boil, then reduce heat and simmer uncovered for 30-35 minutes, stirring occasionally.

To cook chicken: Preheat oven to 400 degrees F. Drizzle or rub a tiny bit of olive oil over chicken and generously season with salt and pepper. Place on baking sheet and bake 18-25 minutes, baking times differ depending on the size of your chicken breast but remember to cook until juices run clean. Alternatively you could use about 3 cups of rotisserie chicken. 

Cool chicken for 5-10 minutes then pull and shred chicken with two forks and add to chili, simmering uncovered for about 20 more minutes or until chili reaches desired consistency. Serve with fresh queso, cornbread or chips if desired. I love topping mine with a little bit of greek yogurt.