Heat oil in a pot; add onion and sauté until pieces are translucent.

In a mixing bowl, stir together the cornstarch and broth.

Gradually add it to the onion, stirring constantly while adding.

Stir in all the other ingredients, except cheese, and bring to a boil.

Reduce heat and simmer for 15 minutes.

Ladle into individual bowls and top with Monterey Jack cheese