To make Crispy Tofu:Cut tofu into 2 slabs. Wrap tofu slabs in paper towel and place between 2 cutting boards. Put some weight like soup cans or cast iron pan, on top of the cutting board and press for 30 minutes (or up to 4 hours).
In a resealable container, combine soy sauce, vinegar, mirin, oil, garlic and ginger. Add tofu and toss to coat. Marinate for at least 30 minutes or overnight.
Preheat the oven to 350°F and coat a baking sheet with cooking spray.
Sift cornstarch over tofu and turn to coat evenly. Spread tofu on baking sheet.
Baking 30~40 minutes or until firm and crispy, turning several times to brown all sides.
To make General Tso's Sauce: Whisk together broth, sugar, soy sauce, mirin, vinegar, sesame oil, corn starch, tomato paste, sambal oelek (if using) in a small bowl. Set aside.
Heat 1tbsp oil in a wok or large skillet over medium-high heat. Add green onions, garlic and ginger, stir fry 1 minute. Add broth mixture and cook for 1 more minute, or until thickened.