Most Vietnamese women in northern Vietnam know how to make dua ca (pickles) well and my mother does, too. I have tried a few times when I was in Nha Trang but just couldn't make it right. Today, I walked pass Hang Muoi street and saw an old woman making it and my mouth started watering.
When I saw the woman hanging Dua vegetables on the side of an electric stand yesterday, I thought it'd be a great shot and I took a photo. Today, when I walked past again, she was sitting there making her specialty, going through the many different processes: the dried Dua veggies are laid in the hot sun for a few hours to wilt, after which they are well mixed with warm water and salt. They should taste a bit salty (no sugar is added). Lengths of spring onion are added and the Dua is ready to eat in 2 to 5 days. If you like the pickles a bit bitter then they can be eaten in a day. If you want to stirfry them, they are best after about four days of pickling.
In Hanoi, many typical Vietnamese restaurants serve stir fried Dua veggies with garlic, a little bit of tomato or sometimes with beef. In my opinion, it's better without beef as it has enough favor; the bit of sourness from the veggies, sweetness from the tomatoes, a little salt from fish sauce or soya sauce. It's a perfect match for beer and to eat with steamed white rice. It's actually a nice option for vegetarians, too...if you can get it without the beef, that is.