Preparation - In a bowl, combine the cooked chicken with the condensed soup, salsa and tapioca; set aside. Tear the soft corn tortillas into small pieces (about 1-1/2" to 2"). Spray the inside of a crock-pot with non-stick cooking spray. Line the bottom of the crock-pot with about one third of the tortilla pieces. Layer about one third of the chicken mixture on top; then about one third of the chopped onion; then about one third of the grated cheddar cheese. Repeat each layer two more times, ending with the cheddar cheese. Cover the crock-pot and cook on low for 6 to 8 hours.