A special thanks to mom for help on this one, again.
Dua Cai Chua, or pickled mustard greens is one of the very common accompaniments to a Vietnamese rice dinner, its clean crisp acidity matching well with any number of savory meat dishes common to the culture. There are many kinds of dua (pronounced like zu-ah), which basically means pickles, but of the varieties of Vietnamese pickles, this is my favorite. Aesthetically pleasing, crisp and in my opinion somewhat healthy, it is an ideal first pickle to introduce yourself (or friends) to.
This post is more on the "art" of the pickle, and this is a rough walkthrough of the steps. I'll revisit this later in an attempt to deconstruct my mother's recipe.
First a very large mixing bowl is filled with cleaned and cut mustard greens, you don't want to have it overflowing.
This is optional, but if you like them, add some thickly sliced onion (about a 1/4 inch, no need for exactness). These actually can be cut again in half after mom informed me later that these were a bit long.
A brine of water, salt and a little bit of sugar is mixed together, boiled and cooled. This is where the art comes in. You just want enough sugar to speed up the fermentation, but it doesn't need to be noticeable. The key is to get the salt to where you can taste it, a bit more than mildly salty and nowhere near very salty. This can be adjusted according to taste - according to mom.
Once cooled to to a comfortable warm temperature where you can hold your fingers in, pour the brine over the vegetable mix, pressing down every so often, perhaps every 30 minutes or so. The ideal is that you will submerge the onions and greens in the liquid for a few hours, at least 3, before transferring.
The greens are then transferred into a sterile jar (with chopsticks for authenticity), pouring brine on top to completely cover. We had to use two jars since I may have went a bit overboard with onions. But that's ok because I like pickled onions.
Put in a warmish location, like the top of your refrigerator for a few days to speed up the fermentation process, testing a piece after a few days. Once it's reached your ideal taste, put in the refrigerator and continue to enjoy until you're done!