If you'd like, use a large, round whole-wheat loaf and cut into wedges.
Stir together eggs, mayonnaise, celery, dry mustard, and curry, if desired, in a medium bowl. Season with salt and pepper.
Spread one side of each slice of bread with mayonnaise. Top half of slices with radicchio, and arugula, if desired; spread with egg salad. Top with remaining bread.
This recipe has been adapted from "Favorite Comfort Food," by Martha Stewart Living. Copyright 1999 by Martha Stewart Living. Reprinted by permission of Clarkson Potter Publishers.