Chimichangas de Pollo

1 (3 1/2 pound) whole chicken
6 cups water
1 medium onion, studded with 2 whole cloves
2 stalks celery
2 large whole garlic cloves, peeled
1 bay leaf
2 tablespoons shortening
1 large onion, thinly sliced
1 garlic clove, minced
1 large tomato, cored and diced
1 jalape