Prepare the noodle dough: Dissolve 2g salt in 100g water. Gradually sprinkle water onto 200g all-purpose flour, stirring occasionally. Once combined, press into a ball and cover. Let rest at least 30 minutes.
Knead the dough using 'abacus string' technique: Press dough into a rectangle. Using the bottom of your palm, press down and smear out, then curl the dough back about 1 inch. Move over and repeat. Fold dough in half, press flat, and repeat the curling motion. Continue kneading for 8-10 minutes. Cover and rest 10 minutes.
Roll and cut noodles: Roll dough into a rectangle about 1cm thick. Cut in half lengthwise, then cut into 1cm wide sticks along the longer side. Coat noodles thoroughly with oil to prevent drying. Arrange neatly, cover with plastic wrap touching noodles, then place in a bag and refrigerate overnight.
Marinate the chicken: Cut chicken leg into roughly 1.5 inch chunks. Combine with 1/4 tsp salt, 1/2 tsp chicken bouillon powder, 1/4 tsp Sichuan pepper powder, 1/8 tsp white pepper powder, 1/2 tsp soy sauce, 1/2 tsp Shaoxing wine, sliced Chinese leek or scallions, dried chili pieces, ginger slices, and optional star anise. Add about 1.5 tbsp oil and mix well. Let marinate while preparing other ingredients.
Make tangse caramel: In a cold wok, combine 5 tbsp oil and 40g rock sugar. Turn heat to medium-high and slowly fry for about 3 minutes until caramel forms and settles at the bottom with a brown hue.
Brown the chicken: Increase heat to maximum, add marinated chicken and marinade to the caramel. Stir continuously with chopsticks to prevent sugar crystallization. After about 3 minutes, chicken should be evenly browned and less sticky.
Add wine and Pixian Doubanjiang: Swirl in a splash of Shaoxing wine or baijiu, reduce heat to low. Add 2 tbsp Pixian Doubanjiang and fry for 1-2 minutes to stain the oil and chicken.
Prepare the braising pot: In a separate pot, add 1 tbsp Chinese 13 spice powder or five spice powder, 1/2 tsp Sichuan pepper powder, 1 tsp salt, 1 tsp chicken bouillon powder, and 300g potato chunks.
Finish braising and cooking noodles: Add the browned chicken mixture to the pot with spices and potatoes. Add water or broth to cover and braise until chicken and potatoes are tender. Meanwhile, pull the refrigerated noodles into thin strands and cook in boiling water until done. Serve the braised chicken and potatoes over or alongside the noodles.