In a large pot, heat the oil over medium heat. Add the onion and saute for a few minutes. Add the celery and cook for a few more minutes.
Add the ground beef, break up and brown. Once the meat is browned add the peppers and garlic and stir while cooking for a few minutes. Add the tomatoes, beans and spices(everything else, except the cornstarch) and stir well. Bring to a boil, then reduce to a simmer.
Simmer for at least 30 minutes, or for as much time as you have available. Before serving, stir the cornstarch with a small amount of water to make a slurry. Add this to the pot and stir well, then just cook until thickened.
Serve immediately with your favorite toppings, such as grated cheddar cheese and sour cream.