Heat oil in large saucepan over medium-high heat.
Add pepper and onion;
stir fry about 5 minutes.
Add chicken broth, vegetable stock and soy sauce.
Bring to boiling.
Lower heat; simmer for about 5 minutes.
Stir together vinegar, red pepper flakes, salt, pepper, cornstarch*, water and sesame oil in a small bowl until smooth.
Add to soup with fresh snow peas; cook for about 5 minutes or until thickened and bubbly.
Add tofu, frozen snow peas if using, and water chestnuts.
Gently heat through.
* Omit Corn Starch if made for Liquid Diet.