In 2-cup measuring cup, combine broth, soy sauce, brown sugar and cornstarch, until well-blended.
In nonstick 12-inch skillet, heat sesame oil over medium-high heat. Add tofu and cook, stirring frequently (stir-frying), until heated through and lightly browned, about 4 minutes. Transfer to bowl. Add red pepper, green onions, garlic, and ginger to skillet and stir-fry until vegetables are tender-crisp, about 3 minutes longer.
Add mushrooms and stir-fry 3 minutes. Add broth mixture and tofu and stir-fry until sauce has thickened slightly and boils, about 3 minutes.