In a large stockpot over medium heat, sauté onions in oil until tender. Stir in remaining ingredients except sour cream and cheese.
Simmer for 30 minutes, stirring frequently, until heated through. Shortly before serving, add sour cream and cheese. Stir until cheese is melted. If you like a little kick add a few shakes of Tabasco sauce.
Slow Cooker Version: Sautee onion until soft and throw everything except for the sour cream and cheese in a crockpot on low for 3-4 hours. Shortly before serving, add sour cream and cheese. Stir until cheese is melted and add Tabasco sauce if desired.