Soak rice noodles in room temperature water 30 minutes prior to cooking.
In a small saucepan over medium-high heat, whisk together palm sugar, tamarind paste, and fish sauce. Bring to a boil, reduce heat, and reduce for 5 minutes until the sauce thickens and coats the back of a wooden spoon. Remove sauce from heat and set aside.
Heat a cast-iron pan or wok over high heat.
Add pork belly and sear for about 3 minutes.
Add oil, minced garlic, shallots, and turnips, and stir to incorporate.
Move the pork belly to the side of the pan and add the egg. Break the egg up with a spatula or wooden spoon and stir to scramble.
Add soaked rice noodles and stir to evenly incorporate all ingredients, stirring for 1 to 2 minutes.
Add 2 or 3 tablespoons of the reduced sauce and stir.
Add tofu, Chinese chives or green onions, and bean sprouts. Stir to incorporate and remove from heat.
When plating, make a divot in the center of the noodles and add the egg yolk.
Serve immediately with lime, peanuts, more sprouts and chives, and red chiles, if desired.