In a large bowl, combine all-purpose flour and fine salt. Gradually add warm water, mixing with a fork until a shaggy dough forms. Knead the dough on a floured surface for about 8-10 minutes until smooth and elastic. Cover it with a damp cloth and let it rest for 30 minutes.

While the dough rests, cut the firm tofu into even cubes. Toss the tofu in cornstarch to ensure each piece is well-coated. Heat vegetable oil in a skillet over medium-high heat and fry the tofu for about 4-5 minutes on each side until golden and crispy.

In a dry skillet, toast the cumin seeds, Sichuan peppercorns, and coriander seeds over medium heat for about 2-3 minutes until fragrant. Remove from heat and grind into a fine powder.

Roll out the rested dough on a floured surface into a thin sheet. Hand-pull the dough into thin noodle strands. In a large pot, bring salted water to a boil and cook the noodles for 2-3 minutes until al dente, then drain and rinse.

In the skillet used for frying tofu, heat a tablespoon of vegetable oil on medium heat. Add diced onion, minced garlic, and grated ginger. Sauté for about 3-4 minutes until onion is translucent. Stir in the spice mix and cook for an additional minute.

Add the cooked noodles to the skillet, drizzle in chili oil, light soy sauce, dark soy sauce, and Shaoxing wine. Toss gently for 2-3 minutes. Fold in crispy tofu, garnish with scallions and cilantro before serving warm.