1. Soften gelatin in beef broth in a small saucepan. Heat slowly, stirring constantly, until gelatin dissolves; pour into a shallow pan. Chill 30 minutes, or until syrupy.
2. Cut eggs in half, crosswise; carefully remove yolks and place in a small bowl. Mash well with a fork. Blend in mayonnaise, mustard and salt to make a smooth mixture.
3. Fill egg whites with egg mixture(Pipe through a pastry bag with a star tip, if you wish.). Place 2 stuffed eggs into each of 4 custard cups.
4. Spoon gelatin syrup over eggs, dividing evenly. Chill at least 4 hours, or until firm.
5 Unmold by running a thin bladed knife around edge of each cup; dip cups quickly in and out of a pan of hot water. Invert onto lettuce lined salad plates.