Bring the chicken backs and water to a boil over high heat. Skim the scum, then add the onion, ginger and salt. Simmer for about 1 ½ to 2 hours to yield a flavorful stock. Strain, then pick off the meat from the bones. Skim and save the fat from the stock; you should have about ⅓ cup (90 ml) of chicken fat. (Or refrigerate overnight and lift off  the fat layer.)

Wash the rice then set aside to drain for about 20 minutes. Measure out 2 ¼ cups (of stock into a saucepan. Season with fish sauce then bring to a simmer.

Meanwhile, heat 3 tablespoons of the fat in a wide pot over medium heat. Add the rice then lightly fry for 3 to 5 minutes, until chalky and dryish looking. Add the hot stock, stir and let bubble and sizzle. Lower the heat to medium-low. Cover and cook for 2 to 4 minutes. Lift the lid occasionally to stir. When a few craters form at the top, lower the heat to low, cover and let cook for 10 minutes.

As that happens, heat 2 tablespoon of the chicken fat in a skillet over medium heat. Add the celery and cook for about 2 minutes, until slightly softened. Add the chicken and cook for 1 to 2 minutes to heat through. Off heat, season with salt, a sprinkle of fish sauce and black pepper.

Turn off the rice but leave it on the hot burner. Add the celery and chicken. Replace the cover and let sit for 10 minutes to continue cooking. Fluff the rice and stir in the celery and chicken; if the rice is dry, add 1 to 2 tablespoons stock. Let rest 10 more minutes to finish. Taste, tweak, and fluff before serving.