Heat 1 inch oil in a deep skillet to 350°F.

Lower one tortilla into the oil, fry for 30 seconds and fold it loosely around metal tongs.

Fry for 45 to 60 seconds more until puffy and pale gold, then drain it upside down on a rack.

Repeat with the remaining tortillas and keep the shells uncovered.

Reheat the seasoned beef to 165°F and divide it among the shells.

Add lettuce, tomato, cheddar and sour cream just before serving.