In a medium bowl, mix together the butter, yolks, sugar, sour cream, vinegar and rum until smooth. Gradually stir in flour until the dough is thick enough to handle. Turn the dough out onto a lightly floured surface and knead for about 15 minutes.
Put the dough into a bowl and cover with a cloth.
Let it rest in a cool place for an hour.
Heat oil in heavy skillet to 375 degrees F (190 degrees C). To test readiness of oil, put a small piece of dough in it, if it immediately comes to the surface, the temperature is right. On a lightly floured surface, roll the dough out to no thicker than 1/8 inch thickness.
Cut into strips 2 inches wide and 7 inches long.
Cut a 2 inch slit down the center of the strip lengthwise. Pull one end through the hole.
Fry 4 or 5 strips at a time, turning once, until brown.
Drain on paper towels and dust with confectioners' sugar while still warm.
