Combine yolks, sugar, and salt in top of a double boiler. Gradually add milk, mixing well. Cook over boiling water, stirring constantly, until mixture coats a metal spoon. Soften gelatin in cold water; add to milk mixture, stirring well. Remove from heat and let cool. Stir in vanilla.
Beat egg whites (at room temperature) until stiff peaks form. Fold into gelatin mixture. Fold in whipped cream. Spoon filling into Chocolate Crumb Piecrust. Sprinkle with grated chocolate. Chill.