In a cup, whisk together the broth, soy sauce, sherry, and cornstarch. Set aside.
Heat the oil in a large nonstick skillet over medium-high heat. Add the broccoli, garlic, and ginger and cook, stirring constantly, for 1 minute. Add the mushrooms and cook, stirring frequently for 3 minutes or until tender and lightly browned.
Add the tomatoes and tofu and cook, stirring frequently, for 2 minutes or until the tomatoes begin to collapse.
Stir the cornstarch mixture and add to the skillet. Cook, stirring, for 2 minutes, or until the mixture boils and thickens.