Combine the rice flour, tapioca starch, and a pinch of salt in a large mixing bowl. Pour in 3/4 cup boiling water (200 ml), mix well, and knead until you have a smooth, non-sticky dough. Divide the dough into 4 portions, roll each one out thinly, then cut into noodles.

Rinse the pork and slice it thinly. Season with a pinch of salt, fish sauce, a little MSG, pepper, and minced shallot. Peel the shrimp and chop finely. Heat a pot with a little cooking oil, sauté the minced shallot until fragrant, add a bit of annatto oil for color if desired, then add the pork and shrimp and stir-fry until just cooked. Pour in about 5 cups water (1.2 liters). Mix a little fermented shrimp paste with water and add to the pot. Add the noodles and cook until done, then season to taste.