Thursday, May 17, 2012

Lamp shadow sweet potato chips

In Sichuan, quite a number of dishes have the charming name of "lamp shadow," or dengying, which to a Chinese person immediately calls to mind shadow puppetry. The idea is that whatever is being cooked is sliced so thinly that it becomes translucent. Lovely, eh?

There are many versions of this dish, some more fancy and worthy of banquet tables, but today's version is just right for a simple family meal. In fact, I could see this easily taking the place of fries and chips. The ingredients are basically just sweet potatoes and frying oil. A mandoline is used to slice the potatoes, and today you'll learn how to fry things in two stages to achieve crunchy perfection.

Use a mandoline
But first things first. You'll need a mandoline. If you don't have one, go get a cheapo Japanese one. Benriner makes some excellent ones that are almost all plastic except for the blades, so they are light and cost little to make. 

I've tried others, but none beat out the Japanese models, in my humble opinion. They have different models, so see what works for you. In the photos I use another crappy old mandoline that my late mother-in-law gave to me in great confusion after someone gave it to her as a gift (she used a cleaver for absolutely everything), and it has all sorts of different blades, but I think I've basically just used the one for plain slicing.

Once you have that mandoline, look for the hand guard. That is your friend. The blades on a mandoline are razor sharp and will reduce your fingers in a hurry, so use the hand guard.

Thin horizontal slice by hand
If you have mad knife skills, or if you're just not up to having another piece of kitchen equipment rattling around in your drawers, you can do this by hand. In this case, slice off the edge of a peeled potato so that it lies flat. Then, slice it either vertically or horizontally. (You can use this second technique to cut up any leftover pieces from the mandoline, by the way.) Just remember that these potatoes will be rather hard, so use caution.

An optional ingredient here is alum, which helps to increase crispness. This is something that is used a lot in pickling, so you can often find it near canning supplies in Western or, in my case, Japanese markets (see the photo at the bottom). Alum pretty much lasts forever, so buy a box, put it on your pantry shelf, and you will be set for life. But if  you can't find it, don't worry about it, as these chips will still be very good.

Count on about one potato per person. This recipe is for two people, but can easily be multiplied. If you are making these ahead of time, store them in a single layer in the oven heated at the lowest setting, as this will help keep them crisp.

Flavor these chips to match whatever they are being served with and to match the tastes of your guests. I love these punched up with lots of dried chili flakes and toasted ground Sichuan pepper salt, but use just salt if you like, or chopped garlic... hard to go wrong with these, no matter what you do.

Better than bagged chips... by far
Lamp shadow sweet potato chip
Dengying shupian  燈影薯片 
Serves about 2 people

2 long, thin, red sweet potatoes (about 8 ounces)
Large bowl of cool tap water
Tiny pinch of alum, optional
4 to 6 cup frying oil (see Tips)
Seasoned salt of any kind

1. Wash and peel the potatoes. Slice them thinly on a mandoline or by hand (see notes above). Squish the alum between your fingers in the water so that it dissolves and add the potatoes to the water to soak for about 10 minutes while you clean up and prepare for the next steps.

Moisture escaping
2. Set up your frying station with a wok filled with the frying oil on the stove, and nearby place a pair of cooking chopsticks and a Chinese spider or slotted spoon, a small work bowl, and a serving bowl lined with a paper towel. Have the seasoned salt next to the serving bowl, too. Heat the oil over medium high. Keep kids and pets out of the room since you are dealing with lots of very hot oil.

3. Drain the potatoes and rinse well a couple of times under running water. Drain the potatoes and then pat them very dry with a clean tea towel, as the water will otherwise explode in the hot oil. 

4. When the oil is hot enough that the chopsticks immediately foam when they are placed in the oil, add about a third of the potatoes to the oil and swish them around so that they do not stick. Gently fry the potatoes; they will bubble and foam, since at this point they are releasing their moisture. This means, too, that they will shrink alarmingly. As the bubbling subsides and before they start to brown, use the spider to scoop them into the work bowl. Cook the rest of the potatoes the same way in another two batches.
After the first frying

5. Increase the heat under the wok to high. Place the serving plate next to the wok and the spider propped up against the wok. This step needs to be done very quickly, but it is pretty easy as long as you coordinate your motions like this: take a small pinch of the cooked potatoes with your left fingers and drop them in the oil; use your right hand to swirl the potatoes around with the spider; the potatoes will immediately swell up and brown, at which point you use your right hand to scoop them up with the spider and into the waiting serving bowl. Remember to take relatively small pinches of the potatoes, as too many will cool the oil down and clump together; you want to give them room to expand.

6. When all of the potatoes have been fried the second time, toss them with the seasoned salt to taste and serve immediately.

Japanese alum & red sweet potatoes

Used oil is fine for this, as long as it doesn't taste strongly of fish or isn't stale.

Baking potatoes can be used instead of sweet potatoes, if you prefer.

An odd but really good Chinese twist on this is to sprinkle sugar on the fried sweet potatoes. If you add cinnamon, they might become habit forming.

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