Beat egg yolks in a medium size mixing bowl until thoroughly blended. Add milk, flour, sugar, rum and salt; beat with a wire whisk until smooth. Blend in melted butter. Refrigerate for 1 hour. Beat egg whites until stiff, but not dry; fold into batter; combine well. Lightly grease an 8-inch heavy skillet or omelet pan with butter. Place over moderate heat until a few drops of water sprinkled in skillet dance. Stir batter. Remove pan from heat and pour 3 tbsps of batter into the pan; quickly tilt pan in all directions to coat the bottom with batter. Return to heat; cook until lightly browned. Turn; cook for a few seconds on other side. Transfer to a warm plate. Continue in the same manner; stirring batter before making next pancake. Stack pancakes with waxed paper between each one. Keep warm until all pancakes are cooked. Place 1 1/2 tbsps jam in center of each pancake; roll. Place side by side on a platter. Combine hazelnuts and sugar; sprinkle over pancakes. Heat in a 325°F oven for 10 minutes. Makes about 6 servings. These pancakes are great with ice cream and rolled in the same manner and topped with chocolate or butterscotch sauce.