Make a sauce of butter, flour, and stock; add egg yolk diluted with cream, lemon juice, salt, and pepper; then add dissolved gelatine. Dip chicken in sauce which has been allowed to cool. When chicken has cooled, garnish upper side with truffles cut in shapes. Brush over with aspic jelly mixture, and chill. Arrange a bed of lettuce; in centre pile cold cooked asparagus tips or celery cut in small pieces, marinated with French Dressing, and place chicken at base of salad.