Cut tofu in half crosswise and again in half lengthwise. Pierce tofu liberally with a fork.
Place in a shallow dish.
Combine 1 tablespoon oil and 1 tablespoon soy sauce in a small bowl.
Pour soy mixture over tofu; let stand 15 minutes, turning once. Set aside.
Heat a large nonstick skillet over medium-high heat.
Add 1 tablespoon oil; swirl to coat.
Add bell pepper, carrot, and salt; saut 3 minutes.
Remove from pan.
Add remaining 1 tablespoon oil; swirl to coat.
Add garlic and mushrooms; saut 4 minutes.
Add remaining 2 tablespoons soy sauce, broth, and next 3 ingredients. Simmer 3 minutes or until thickened.
Remove from heat.
Remove tofu from marinade; reserve marinade.
Heat a grill pan over high heat. Coat pan with cooking spray.
Add tofu to pan; cook 3 minutes on each side, basting occasionally with reserved marinade. Arrange 1 tofu steak on each of 4 plates; top each serving with about 1/3 cup carrot mixture and about 2 tablespoons mushroom mixture.