The first time I had food flavored with Yu Hsiang was at Mary Chung's in Central Square, and it immediately became one of my favorites. The sauce is a sweet and hot and garlicky, and goes well with just about any kind of stir fry. I attempted to make it at home, and the result was so successful I made it again the next day.
The way I prepared this, there were two components to the sauce. The first was the ingredients that were fried in oil to start the dish, and the second was the liquid elements added at the end.
The ingredients that went into the oil were 3 chopped scallions, two cloves of garlic, and about an inch of minced ginger, along with a spoonful of chili-soybean paste from the Asian market. If you don't want to use (or can't find) the soybean paste, you can use chili-garlic sauce or just chilis to provide the heat.
After a few minutes of frying the flavorings, I added the beef. I used thin-sliced beef meant for steak sandwiches which sliced again into thin strips, resulting in ribbons of meat. I also prepped some vegetables, cutting them into stir-fry sized pieces. You can use whatever you have on hand - I used cubanelle peppers, carrots, onions, and zucchini.
For the liquid portion of the sauce, I mixed soy sauce, rice wine and rice vinegar in about a 2:1:1 ratio. I added a spoonful of brown sugar for sweetness and a spoonful of cornstarch for thickening.
When the beef was done, I added rice noodles (fresh and already cooked - if you use dry noodles, soak/cook them first) along with the vegetables, sauce, and some chopped basil. I kept the heat on for about a minute, and let the heat already present take care of the rest.
The noodles ended up just as I had hoped - sweet and tangy and garlicky. I ate them with some sauteed chard and some quick pickled cucumbers. There are a fair number of ingredients in this, but it doesn't take much longer to prepare than a standard stir fry. Cutting up the garlic and ginger doesn't take much time, nor does mixing the wet ingredients. I expect this to become a part of my standard rotation!