Press the 10 oz block of firm tofu for about 15 minutes to remove excess water, then tear it gently into bite-size pieces with your fingers.
In a bowl, toss the torn tofu with 2 Tbsp soy sauce, stirring gently to coat; let rest a couple minutes and drain any excess liquid.
Add 2 Tbsp cornstarch to the tofu and toss gently until each piece is lightly coated.
Heat 3 Tbsp vegetable oil in a skillet over medium-high heat. When hot, fry the tofu pieces in a single layer, turning so each side cooks 2–3 minutes, until golden and crisp. Transfer to paper towels to drain.
Wipe the pan, add 1 Tbsp vegetable oil, and warm over medium heat. Add the minced garlic and minced ginger and cook, stirring constantly, 1–2 minutes until fragrant without browning.
Pour in 1/4 cup soy sauce, 1/4 cup lukewarm water, 2 Tbsp cane sugar, 2 tsp molasses, and 1/2 tsp Sriracha; stir and bring the mixture to a gentle boil.
Mix 1 Tbsp cornstarch with 3 Tbsp water to make a slurry, then whisk it into the simmering sauce and stir constantly until the sauce thickens.
Add the fried tofu to the sauce and toss gently to coat each piece evenly; cook briefly so the tofu heats through and is evenly glazed.
Serve immediately, optionally topped with chopped scallions and sesame seeds if available.