This is my FAVOURITE noodle dish to eat when I get home. Not so much mee suah or laksa or kolo mee. 'Hoongan', 'kampua', 'cha chu mien' and 'kueh chap' are what I look forward to. This noodle is mainly SOUR and sour to the max from the preserved vege.
There is no hard and fast rule what you put as fillings. The important thing is to get the soup right. You can use sliced chicken or pork or even fish. Fishballs or fishcakes work well too.