Press the firm tofu for about 15 minutes to remove excess water using a tofu press or by placing it between paper towels with a weighted pan on top.
Tear the pressed tofu into bite-size pieces with your fingers, starting by halving or cutting larger chunks and then gently pulling into pieces; avoid smashing.
In a small bowl, whisk together soy sauce (or tamari), balsamic vinegar, maple syrup, dried thyme, smoked paprika, and molasses until combined to make the marinade.
Place the tofu pieces in a bowl, pour most of the marinade over them, and stir gently to coat. Reserve the excess marinade. Let the tofu rest in the marinade for 15 minutes.
After marinating, drain the tofu, saving the remaining marinade. Sprinkle 1 tablespoon cornstarch over the tofu and toss gently to coat each piece evenly without breaking them.
Heat 3 tablespoons vegetable oil in a large skillet over medium-high heat. When hot, add tofu pieces in a single layer and fry, turning as needed, about 2–3 minutes per side until golden and crispy. Transfer to paper towels to drain.
Whisk the remaining cornstarch into the reserved marinade until smooth and lump-free.
Pour the marinade into the same skillet and bring it to a boil over medium heat, stirring until it thickens into a glaze.
Add the fried tofu back to the pan and toss or stir gently to coat each piece evenly with the sticky glaze. Cook 1–2 minutes to heat through and set the sauce, then serve.