Cook pasta according to package directions. Drain pasta, rinsing with cold water; set aside.
In large skillet, saute chicken and garlic in butter until chicken juices run clear; sprinkle with seasoned salt. Remove chicken with a slotted spoon; set aside.
In same skillet, saute water chestnuts for 2-3 minutes. Meanwhile, drain oranges, reserving 1/2 cup juice. In a large serving bowl, combine oranges, pasta, chicken, water chestnuts, peas, mushrooms, carrots and onions.
In a quart-sized jar or similar container with tight-fitting lid, combine the oil, vinegar, soy sauce, garlic, sugar, honey, ginger and reserved mandarin orange juice; shake well. Pour over pasta mixture and toss. Sprinkle with sesame seeds.