Start by draining the firm tofu and pressing it to remove excess moisture. Wrap the tofu in a clean kitchen towel and place a heavy object on top for about 15-20 minutes.
Once pressed, cut the tofu into bite-sized cubes.
In a mixing bowl, toss the tofu cubes with 2 tablespoons of corn starch until evenly coated.
Heat 4 tablespoons of vegetable oil in a frying pan or wok over medium-high heat. Add the tofu cubes and fry until golden and crispy on all sides, about 10-15 minutes. Remove from the pan and drain on paper towels.
In the same pan, lower the heat to medium. Add 1/2 cup soy sauce, 1/2 cup lukewarm water, 2 tablespoons of cane sugar, 2 teaspoons of molasses, 1 teaspoon of minced ginger, 2 cloves of minced garlic, and 1 teaspoon of sriracha. Stir well and let it simmer for about 5 minutes.
In a separate bowl, mix 1 tablespoon of corn starch with 3 tablespoons of water to create a slurry. Gradually pour the slurry into the simmering sauce, stirring constantly until it thickens.
Add the crispy tofu back into the pan with the sauce and gently toss to coat. Cook for an additional 2-3 minutes.
Remove from heat and serve hot over steamed rice or noodles, garnished with green onions if desired.