Rinse the bean sprouts with cold running water, drain, and set aside. Remove the roots if desired.: The cold rinse removes any grit and firms up the cell structure of the bean sprouts , giving them a bright feel and clean flavor; you should hear a faint, watery rustle as you drain them, which tells you they are well rinsed. Do this step right away so they are ready when the tofu is done; fresh, crisp sprouts will have a slightly cool, succulent bite. If they smell off or look slimy, discard them to avoid an unpleasant final dish. Avoid soaking them for long periods because that dilutes flavor and weakens the crunch.
Heat up a wok and add some cooking oil for pan-frying the tofu. Once the oil is fully heated, pan-fry the tofu until they turn light brown on the surface. Transfer the tofu to a dish lined with paper towels.: When the oil in the wok shimmers and moves like quicksilver, it is ready; that heat gives the tofu an immediate sizzle and a golden surface. Listen for a confident sizzle as you add the rectangles, which signals proper searing. The visual cue is a developing golden brown edge within the first minute to minute and a half. If the oil smokes heavily, reduce heat slightly to prevent burnt flavor. A common mistake is using low heat which causes the tofu to stick and become pale rather than browned.
Leave about 1 tablespoon of oil in the same wok, stir-fry the garlic until aromatic, then add the tofu back into the wok for a few quick stirs. Add the bean sprouts, soy sauce, and scallions, and stir for a few more seconds. Dish out and serve immediately.: You will see crisping and light caramelization, with small brown patches forming around the edges; that Maillard reaction is what gives the tofu a nutty, savory note. Turn the pieces a few times to get even color, but avoid constant flipping which prevents proper crust formation. The tofu should feel firmer to the touch as the surface cooks, while the interior remains tender. Avoid overcrowding the pan because that traps steam and yields soggy surfaces.
Transfer the tofu to a dish lined with paper towels: Placing the hot pieces on paper towels removes excess oil and keeps the exterior pleasantly crisp without becoming greasy; you should notice a small residual sizzle as oil drains off. This rest also helps the tofu hold shape when it goes back into the wok during the final toss. Leaving them in the sun of the pan will continue cooking and can dry them out, so transfer promptly. A slip people make is stacking pieces which traps steam and ruins the crust.
Leave about 1 tablespoon of oil in the same wok, stir-fry the garlic until aromatic, then add the tofu back into the wok for a few quick stirs: That single tablespoon of oil becomes the flavor carrier for the garlic , releasing fragrant oils that perfume the whole dish; you will smell a warm, toasty garlic aroma within seconds. Reintroducing the tofu at this point allows it to pick up those aromatics without overcooking. Keep the motion brisk and the heat moderate so the garlic does not burn. A common error is letting the garlic brown too much, which adds bitterness rather than a sweet aromatics.
Add the bean sprouts, soy sauce, and scallions, and stir for a few more seconds: When the bean sprouts hit the wok, they should sizzle briefly and glisten as the soy sauce makes contact, creating little pockets of savory shine; the motion should be quick to maintain crunch and freshness. Toss everything together until you see the sprouts wilt only slightly, and the scallions soften just a touch, which keeps their green character. The final visual is a glossy, vibrant mix with lightly browned bits of tofu and glossy strands of bean sprouts . If you leave them in longer, the sprouts will become limp and watery, so finish swiftly and serve right away.