1 pound extra firm tofu (you can use firm, but extra firm is best)
2 tablespoons reduced-sodium soy sauce, plus more for serving
1 tablespoon seasoned rice wine vinegar
1 teaspoon toasted sesame oil
1 tablespoon canola oil
2 small onions, cut into wedges
9 ounces button mushrooms, quartered
1 large red bell pepper, ribs and seeds removed, cut into chunks
1 1/4 pounds bok choy, cut into small pieces
1/4 pound snow peas, trimmed
3 medium patty pan squash, cut into chunks
1 teaspoon cornstarch dissolved in 2 teaspoons cold water
1.Halve tofu block lengthwise; slice each half into 8 rectangles. Arrange on a paper towel-lined baking sheet; top with more paper towels and another baking sheet. Weight with canned goods or a skillet for at least 20 minutes.
2.Transfer tofu to a shallow dish. In a bowl, whisk together soy sauce, vinegar, and sesame oil with 1 tablespoon water; pour over tofu. Marinate 5 minutes (or longer, if you can) (reserve marinade).
3.Heat canola oil in a non-stick pan over high heat. Cook tofu until golden, 1 to 2 minutes per side. Set tofu aside.
4.Stirring constantly, cook onions in pan over high heat until browned. Add mushrooms; cook approx. 2 minutes. Add red pepper and bok choy stems; cook until done, but still firm, approx. 3 minutes. Add peas, bok choy leaves and squash cook 1 minute. Add marinade, cornstarch mixture, and tofu. Cook until heated through. Season with soy sauce as desired. Serve with brown rice.