Combine yolks and egg in a small mixing bowl; beat well. Gradually add chicken broth, beating until well blended. Pour mixture into a well-greased 10- x 6- x 2-inch baking dish. Place baking dish in a 13- x 9- x 2- inch baking pan. Pour hot water into pan to a depth of 1 inch.
Bake, uncovered, at 350° for 25 minutes or until a knife inserted halfway between center and edge of custard comes out clean. Remove baking dish from pan. Cool custard to room temperature in baking dish. Cut custard into various shapes with miniature aspic cutters. Remove from dish.
Use Royal Custard as a garnish for hot broths or consommés.