mexican black bean & sweet potato chili

Ingredients

• 3 tablespoons olive oil, extra virgin
• 1 medium onion, chopped
• 2-3 medium peppers, chopped (preferably poblanos but bell will work)
• 1 tablespoon ground cumin
• 1 tablespoon dried oregano
• 1/2 bottle beer (preferably an amber mexican beer like dos equis)
• 3 medium sweet potatoes, chopped (skin left on)
• 1 28 ounces can crushed tomatoes (preferably fire-roasted)
• 2 cans black beans
• 2 cans other beans (great northern, red, pinto, even chicpeas will work)
• 2 - chipotle chili peppers, diced (from the can)
• 1 tablespoon adobo sauce (from canned chipotles)
• - sour cream or plain yogurt, optional
• - cilantro, optional
• - avocado, optional