Marinate the fish fillets with cornstarch, salt, pepper, and rice wine for 10 minutes.
Meanwhile, prepare the soup broth. In a large, deep pot, heat some oil over medium-high heat. Stir-fry minced ginger, garlic, and chopped fresh chillies until fragrant.
Transfer soybean sprouts and pickled mustard greens to the pot. Stir-fry for 2-3 minutes.
Pour in water, then season with chicken dense soup and sugar. Mix well.
Add in wide glass noodles, ensure they are fully covered in the broth, then cover with a lid. Cook for 10 minutes, stirring occasionally to prevent the noodles from sticking to the bottom of the pot.
Add in tofu, fish fillets, and dried hot chilli peppers. Stir to combine and cook for another 2-3 minutes.
Meanwhile, heat the Sichuan peppercorn oil in another pot. Add in Sichuan peppercorns, and stir-fry till fragrant. Turn off the heat and set aside.
When the fish fillets are cooked, pour over the heated Sichuan peppercorn oil on top.