Heat 1 tablespoon vegetable oil in a Dutch oven over medium heat. Add 1 medium chopped onion and 2 cloves minced garlic and cook 5 minutes or until softened. Add remaining ingredients (except garnish) and mix well. Bring to a boil. Reduce heat; cover and simmer 30 minutes stirring occasionally. Garnish with sour cream and/or cheddar cheese if desired.