Stir 1 teaspoon granulated sugar into warm milk and sprinkle with yeast.
Let stand 5 minutes or until the surface is frothy.
Stir gently to moisten any dry particles remaining on top.
Sift flour, remaining granulated sugar and salt into a large bowl.
In a medium bowl, lightly beat oil, egg yolks and rum; stir in yeast mixture, Pour Into flour mixture, beating until a light dough.
Cover and let rise in a warm place 20 minutes.
On a floured surface, roll out dough 1 inch (2.5 cm) thick.
Cut out 2-3/4-inch (6.5-cm) rounds.
Place a teaspoonful of jam on each round; draw dough together carefully over jam and pinch firmly.
Let doughnuts rise in a warm place 15 minutes.
Heat oil for frying to 360°F (180°C) in a deep-frying pan.
When doughnuts have risen, place them smooth side down in hot oil.
Cover and cook 3 minutes, turning until golden brown all over.
Drain doughnuts on paper towels.
Sift powdered sugar over hot doughnuts.