1 14-oz. block firm or extra-firm tofu, drained
3 Tbsp. soy sauce
3 Tbsp. mirin (sweet Japanese rice wine)
1 tsp. toasted sesame oil
¾ tsp. gochugaru (coarse Korean red pepper powder) or other mild red pepper flakes
2 Tbsp. grapeseed or vegetable oil, divided, plus more for drizzling
1 small garlic clove, finely chopped
1 tsp. finely chopped peeled ginger
Toasted sesame seeds and cooked rice (for serving)
Wrap tofu in a clean kitchen towel and place on a rimmed baking sheet. Weigh down with a heavy object (a couple of heavy cans works well) and let sit 10 minutes. Unwrap tofu and slice in half lengthwise, then cut crosswise into 6 sections to create 12 squares.
Whisk soy sauce, mirin, sesame oil, gochugaru, and 3 Tbsp. water in a small bowl to combine; set sauce aside.
Trim dark green top from scallion and thinly slice; set aside. Thinly slice remaining white and pale green parts of scallion. Heat 1 Tbsp. grapeseed oil in a nonstick skillet over medium-high. Carefully add tofu in a single layer and lightly season with salt. Cook, undisturbed, until golden brown, about 5 minutes; turn over and cook until golden brown on other side, about 5 minutes. Transfer tofu to a plate; reserve skillet (no need to wipe out).
Heat remaining 1 Tbsp. grapeseed oil in reserved skillet over medium. Cook scallion white and pale green parts, garlic, and ginger, stirring, until softened but not browned, about 1 minute.
Return tofu to skillet. Pour in reserved sauce and bring to a simmer. Reduce heat to medium-low and cook, turning tofu once or twice and occasionally spooning sauce over, until sauce is reduced by about half, about 4 minutes.
Transfer tofu to a large plate, spoon sauce over, and sprinkle with sesame seeds and reserved scallion top. Serve with rice alongside.