1. Heat a large skillet over medium-high heat. Add 1 tablespoon peanut oil to pan, swirling to coat. Sprinkle 1/8 teaspoon salt over pork. Add pork to pan, and sauté for 2 minutes or until browned on all sides. Remove pork from pan. Add carrot and celery to pan, and sauté for 2 minutes or until lightly browned, stirring frequently. Add carrot mixture to the pork.
2. Add remaining 1 tablespoon peanut oil to pan, swirling to coat. Stir in green onion bottoms, garlic, and ginger; cook for 15 seconds, stirring constantly. Add rice, stirring well to coat rice with oil; cook, without stirring, for 2 minutes or until edges begin to brown. Stir rice mixture, and cook, without stirring, an additional 2 minutes or until edges begin to brown. Make a well in center of rice mixture. Add egg; stir-fry for 30 seconds or until soft-scrambled, stirring constantly.
3. Return the pork mixture to pan. Stir in mirin, and cook for 1 minute or until mirin is absorbed. Stir in the remaining 3/8 teaspoon salt, soy sauce, sesame oil, and pepper. Remove from heat, and stir in bean sprouts and water chestnuts. Sprinkle with green onion tops.
Total time is 4 hr. 24 min. if you don't have leftover chilled rice.