In a large saucepan or Dutch oven over medium heat, warm the olive oil. Add red onion and bell pepper and sauté until vegetables are soft, about 5-7 minutes. Add garlic and sauté for another 30 seconds. Add chili powder, cocoa powder, smoked paprika, cumin, oregano, salt, and chipotle pepper and sauté for another 30 second or until the spices are fragrant and have coated the vegetables. Pour in kidney beans, fire-roasted tomatoes (with their juices), and vegetable stock
Turn heat to medium-high, bring to a boil, then turn heat down to medium-low, cover, and simmer for 20 minutes. Remove the lid and simmer until the chili thickens and most of the liquid has cooked off, about 5-10 more minutes. Remove from heat and let cool slightly. Season to taste with salt and pepper. Ladle into bowls, add toppings, and serve.