Soften gelatin in 1/2 cup cold water. Place in low heat and bring almost to a boil, stirring to dissolve. Beat egg yolks and sugar until very light. Stir gelatin into egg mixture, cool and gradually add rum. Whip cream until it stands in soft peaks, then fold into gelatin mixture. Cool until mixture begins to set, then spoon into crust and chill for 1 hour. Grate unsweetened chocolate and sprinkle on top of the pie. CRUST: Press and chill.