Preheat the oven to 350 F.
Spread the uncooked rice evenly on a sheet pan and toast in the oven stirring every 10 minutes for a total of 30 minutes until the rice is golden brown.
Allow to cool to room temperature then grind to a powder in a spice grinder. Set aside.
Prepare the broth: In a 4-quart stockpot, add the water, black and white pepper, lemongrass, ginger, and season lightly with salt.
Bring the mixture to a boil, reduce to a simmer and cook for 15 minutes.
Add the fish fillets and bring the mixture to a simmer and cook the fish gently for 15 minutes.
Using tongs and a slotted spoon, carefully lift the fish out of the broth and reserve for later.
Strain the broth, rinse the pot and pour the strained broth back into the pot.
Heat over medium heat and bring to a simmer.
In a small bowl, whisk together the powdered rice and a cup of broth until no lumps remain.
Stir the mixture into the broth and bring to a simmer until it thickens slightly.
Make the soup: In a wok or large skillet, heat the oil over high heat.
Add the lemongrass, garlic and ginger, and stir-fry for 1 minute.
Add the cooked fish and turmeric, and mash into a paste using the back of a spoon.
Pour the contents into the broth and bring to a simmer.
Add the red onions and fish sauce and cook for 10 minutes.
Season with salt and keep hot until ready to serve.
Cook the noodles: Bring a separate pot of water to a boil.
Add the noodles and cook until tender, 3 to 4 minutes.
Drain the noodles and rinse under cool water.
Shake off any excess water and divide the noodles among 4 bowls.
Ladle the soup over the noodles and top each bowl with cilantro, a hard-boiled egg, lime wedges and thinly sliced red onion.