Slice tofu into 1/2-inch thick slabs. Line a baking sheet with two layers of paper towels; arrange slabs of tofu in a single layer and cover with two more layers of paper towels. Place another baking sheet on top, then set a reasonably heavy weight on the pan (I used a dutch oven, you can use books or cans of vegetables evenly distributed on top of the baking pan). Let tofu drain for 20 to 30 minutes, then remove weights and paper towels.: The pressing stage yields a denser, meatier texture that bakes up crisp rather than steamy. You will notice droplets of water appearing on the paper towels as the block compacts, and the block will feel firmer to the touch when it is ready. This matters because excess moisture prevents browning, leaving the surface pale and soft rather than golden. A common mistake is skipping the weight or using too little time, which results in soggy bites; be patient and check that the towels are soaking up water periodically.
While tofu is pressing, preheat oven to 400 degrees F. Line a baking sheet with parchment paper to keep the tofu from sticking (unfortunately foil just doesn't work as well here).: Preheating ensures the moment the tofu hits the oven it begins to firm up and dry on the surface, promoting even browning. You should smell the faint warm, toasty scent of the oven as it reaches temperature. Using parchment reduces sticking and helps the underside brown evenly. One pitfall is placing tofu onto a cold sheet or into an oven that is not fully heated, which can make pieces steam instead of roast; let the oven reach temperature before baking.
Cut tofu slabs into strips then again into 1/2-inch cubes. Place cubes in a mixing bowl. Add soy sauce, sesame oil, and chili garlic sauce and gently toss until evenly coated. Sprinkle with cornstarch and toss until tofu is coated and no dry traces of cornstarch are visible.: When you dice and marinate the tofu , the aroma of sesame and soy will start to come forward, and the cubes will glisten slightly from the oil. The cornstarch helps create a lacy crispy layer as it bakes, sealing in moisture. You want an even dusting of cornstarch so each piece browns uniformly; clumps of cornstarch will leave powdery spots. Avoid over mixing aggressively, which can cause the cubes to crumble.
Transfer to prepared baking sheet, arranging tofu in a single layer so that no pieces are touching.: Spacing is crucial for airflow and crisping, you should see the pieces sitting with small gaps like little islands. As they roast they will dry and take on color, and if crowded they steam and get limp instead. Place them in a single layer and give each piece its own space to brown. A frequent error is piling pieces too close together to save space, which prevents crisping and reduces the golden color you want.
Bake for 10 minutes; flip tofu pieces using tongs or a spatula. Bake for another 10 to 15 minutes or until golden brown.: During baking you will hear faint crackles as moisture leaves and the cornstarch sets into a crust, and the kitchen will fill with nutty, toasty notes. Flip at the halfway mark to ensure both sides achieve that deep golden color. The final visual cue is even, golden brown edges and a slightly chewy interior. If you pull them too early they will be pale and soft, and if you leave them too long the exterior can get overly dry and the centers may lose tenderness.
To make peanut sauce, in a bowl whisk together peanut butter, soy sauce, sesame oil, sugar, rice vinegar, garlic and ginger until smooth. Drizzle in water, 1 tablespoon at a time, until the sauce has a nice thick yet drizzle-able consistency (you may not need all the water depending on how thick you like it).: As you whisk, the sauce will become glossy and fragrant, releasing the tang of rice vinegar and the warmth of grated ginger . Watch the texture carefully, adding water slowly so the sauce stays creamy rather than thin. Taste for seasoning and adjust the chili garlic to control heat. A common misstep is adding too much water too fast, producing a watery sauce that won’t cling to the filling.
Cook rice noodles according to package instructions. Drain and rinse with cold water.: Properly cooked rice vermicelli noodles should be tender but not mushy; rinsing in cold water stops the cooking and prevents clumping. You will feel their slippery texture and see them separate into delicate strands. Overcooking leads to limp, gluey noodles that soak up too much sauce, so monitor the package time closely and taste a strand before draining.
Arrange pieces of lettuce on plates. Top with a small pile of rice noodles and pieces of baked tofu. Drizzle generously with peanut sauce, then sprinkle with green onion, fried shallots and sesame seeds as desired.: As you assemble, contrast is everything, stacking soft noodles, warm tofu , and cool lettuce . The sauce should shimmer on top and the garnishes provide a final crunchy, aromatic punctuation. Serve immediately so the lettuce remains crisp and the tofu retains its contrast. A common issue is assembling too far ahead, which can make the lettuce soggy and dull the textures you worked to create.