Heat your oil in a pan and add the onion. Sauté for 5-6 minutes until the onions begin to soften, then add the garlic and cook for another minute.
Add the tomato paste, chipotle paste (if using), and seasonings, and cook them into the onions for 2-3 minutes, until the herbs and tomato paste are fragrant.
Add the black beans, pinto beans, and kidney beans, and the chopped tomatoes, the chopped cilantro stems, and stock.
Stir everything together and leave your three-bean chili to simmer for 15 - 20 minutes, stirring occasionally. Taste and adjust your seasoning as needed.
Serve with your preferred toppings and sides!
