酸菜魚, or suān cài yú, is more of the more economically-named dishes on the Chinese menu. 酸菜 is pickled mustard greens, and as mentioned a couple of weeks ago, 魚 is fish. It should be easy enough then to deduce that 酸菜魚 involves both pickled greens and fish, but the part that usually goes unmentioned in the name of the dish is that it also involves enough broth/stock that it's most sensibly translated as "fish soup with pickled greens".
Furthermore, it also comes in both spicy and non-spicy versions, and it's not always clear which one you're going to get. However, if you order it in a Sichuan restaurant, for example, you'll probably end up with a spicy one! The one pictured above is a non-spicy version that I ate at my local Chinese restaurant, Royal Palace, which specialises more in northern Chinese food. I also have a photo of a version I ate at Red & Hot, which is a Sichuan restaurant; this one was not only pretty spicy, but the broth was richer and the fish was in fillets rather than the bone-in pieces used at Royal Palace. (This one was listed on the menu as 風味酸湯魚/fēng wèi suān tāng yú, which means something like "local-flavour sour soup with fish".)
English-language recipes for 酸菜魚 are few and far between on the internet. Angie's recipe looks plausible, as does this somewhat idiosyncratically-translated one from chinesefoodfans.com. Both seem to be of the spicy type. This YouTube video (in English) offers a less-spicy version which looks more similar to the one pictured above. I've made a transcript of the video for those who can't or prefer not to listen to it.
I'm afraid I can't give a personal opinion of any of those three recipes, since I only managed to locate the right kind of 酸菜 a couple of days ago (from See Woo in London's Chinatown), and haven't had time to cook since. (This dish was a last-minute replacement for the one I'd originally intended to feature today, necessary because of the unexpected closure of the restaurant where I'd planned to sample a dish known as tiger salad. Apologies for the disorganisation!)