The potato flakes make a full-bodied filling, perfect for piping. One basic recipe makes three variations to chill overnight.
Cut eggs in half lengthwise. Remove yolks. Process yolks, mayonnaise, and next 4 ingredients in a food processor until smooth, stopping to scrape down sides. Stir cooked and chopped shrimp, horseradish, and minced green onions into egg mixture.
Spoon filling into egg whites. Cover and chill up to 8 hours. Garnish, if desired.