Salvadoran Pupusas with Curtido

Ingredients
Curtido (pickled cabbage) Pork and Potato Filling Corn Dough
 * 1 medium cabbage, shredded
 * 2 carrots, shredded
 * 1 small red onion, sliced thin
 * 4 cups cider vinegar
 * 4 cups water
 * 1 tablespoon dried oregano leaves, crushed
 * 2 teaspoons crushed red chile flakes
 * 1 red bell pepper or 4 ajies dulces (sweet red peppers), sliced thin
 * 1 tablespoon salt
 * 3 pounds pork butt, trimmed and cut into small pieces
 * 1 teaspoon salt
 * 1 pound tomatoes (about 3 medium)
 * 1/2 small white onion, sliced
 * 1/2 teaspoon dried oregano leaves
 * 1/4 teaspoon gound black pepper
 * 3 whole cloves
 * 1 large russet
 * 4 pounds masa (freshly ground corn dough)
 * 1 cup vegetable oil

Directions

 * 1) Preparing the curtido: In a large bowl, combine the cabbage, carrots, onion, vinegar, water, oregano, chile flakes, red bell pepper, and salt until well mixed. Trasfer to a glass or plastic 1-gallon jar. Secure with the lid and agitate to mix well. Let marinate at least 1 day. Makes 1 gallon. This mixture will keep up to 1 month in the refrigerator.
 * 2) Preparing meat for filling: In a small pot, combine the pork with water to cover by 2 inches and salt to season. Bring to a rapid simmer. Partially cover and cook until the pork is tender and the water has almost evaporated, about 40 minutes. Uncover; reduce the heat to very low and let the pork fry in its own fat until golden. Remove from the heat.
 * 3) Simmering the filling: Put the tomatoes, onion, oregano, black pepper, and cloves in a blender container. Puree until smooth. Pour the blender contents into the saucepan with the pork. Place over medium heat, stirring the puree with a wooden spoon to loosen bits of browned pork on the bottom of the pot. Remove from the heat and, using 2 forks, shred the meat. Bring the mixture to a boil again. Lower the heat and cook uncover over medium heat for 10 minutes, or until thickened.
 * 4) Finishing the filling: Place the potato in a small pot with water to cover. Bring to a boil and cook until tender, 20 to 30 minutes. Remove from the heat, drain, and peel. Mash the potato or press it through a sieve. In a bowl, combine the pork mixture with 1/2 to 3/4 cup of the mashed potato; mix thoroughly. Makes about 4 cups filling.
 * 5) Forming and cooking pupusas: Mix the masa with the oil until very soft. Form into 25 small balls and cover with a damp cloth. Pat each ball with the palms of your hand until flattened. Place a generous tablespoon of meat mixture in the center of each round. Carefully enclose the filling by pressing the edges of the masa up over the filling. Press the edges of masa together to seal the ball. Lightly pat the masa ball (with enclosed filling) until flattened to 3/8-inch thickness. Place the pupusas on a heated greased grilled; cook until speckled brown. Turn once and continue coocking until speckled and puffed. Remove; top with curtido and serve.