Lip-smacking sourdough onion rings recipe, excellent use of pour-off

The other week I was browsing around old posts on one of my favourite food thoughts sites, Joe Pastry, and found an idea that was a bit of an epiphany. Sourdough onion rings! In fact, sourdough batter fried anything! (Apple fritters, anyone? Must, must try. Perhaps even Bramley apple fritters? hmm...)

If I’m not baking sourdough bread every weekend my starter gets a bit neglected and not in the best of spirits. It’s not much of a problem as it is nicely revived after a couple of feeds but I prefer keeping it fairly active and healthy, with the idea it might help it ward off mold and off-notes. The main problem is the pour-off. I hate wasting starter and worry about the effect on plumbing even if the pour-off is thoroughly diluted and chucked down the loo instead of the kitchen sink. Pancakes are well and good, as are waffles made with sourdough batter, but it’s good to have a bit more choice.

Looking around, regular onion ring recipes often include eggs in the batter. Some use them simply mixed in with flour and others have the yolks mixed in first and the whites whipped to stiff peaks before folding into the batter, yet more batters use beer.

Sourdough starter has a couple of good things going for it as use as a batter aside from the fact you may have been about to throw it out anyway – the processes of the yeast and bacteria thriving in the starter produce lactic and acetic acids and alcohol and so there is a wonderful vinegary tang already in the batter, before, as any self-respecting Brit would, the fried product is liberally doused with vinegar at the table. I would go as far as to say that depending how sour your starter is when you poured off the portion to use for this recipe, you might not even need additional vinegar at all... just sayin'.

Comparing a few sourdough onion ring recipes and attendant photos, it seems the key to having a nice thick bubble of airy batter around your ring, that adheres properly to the onion at all stages of preparation and eating, is twofold – dredge the raw rings in flour before dipping in the batter and have your oil hot enough for frying. Most recipes state the oil should be at least 175°C (340°F), and I've also seen 190°C (370°F) recommended.

Don't crowd the pan

Very excited to try this out, I sourced a little tempura pan at a local supermarket. It was about 1,800 yen (just over 10 quid), simple design with a cute rack for the temporary resting of fried goods. Of course you can use any deep fat fryer you might have, indeed the electric ones are also much safer than these old fashioned pan-of-boiling-oil setups.

Recipe for sourdough onion rings

• About 240ml (1cup) of cold sourdough starer
• About 60ml (quarter of a cup) of cold sparkling water
• About 60g (half a cup) of flour
• A large onion
• Oil for frying (canola, etc)
• Salt and pepper
• Any exciting seasonings you want to add such as paprika, garlic salt, chilli flakes etc.

All measurements approximate, adjust depending on how thick and sour your starter is. You want a consistency thick enough to cling to the onion, similar to pancake batter. Starting with a cup of sourdough starter gave me enough batter for a bit more than just 1 large onion. Original recipes referenced include the Joe Pastry example and this from La Brea Bakery's Nancy Silverton.

Method:

1. Slice your onion as thick/thin as you'd like, my slices are about 1 cm thick and I separated out the rings so they had about 2 layers each. I left the smaller center rings intact as little solid discs.
2. Put the rings into a shallow dish of seasoned flour, turning them over to have the flour stick to the juicy bits of the sliced onion.
3. Mix your starter with the sparkling water in a smallish bowl along with any seasoning you want to use. I've seen recommendations to rest the small bowl inside a larger bowl that contains ice water/rest a metal bowl on a frozen gel pack, or like when you make tempura you could put a couple of ice cubes directly into the batter to keep it cold. The idea is that cold batter helps to create a crispy fry. I used the 'bowl over an ice water bath' method for these rings but I think you’d also probably get quite good results by using cold ingredients fairly quickly.
4. With your oil between 175 – 190°C (340-370°F. Use an infrared thermometer to be sure, or test the oil. The oil won’t be bubbling until the food is introduced), reduce the heat if necessary to avoid going too hot and take a slice of onion from the flour, drop it in the starter mix and turn to coat if necessary. Lower them one by one into the hot oil carefully using cooking chopsticks or tongs. 
5. Use a metal strainer or slotted spoon to turn the rings over and fry for about 3 minutes or until they are slightly golden. Note that the temperature of the oil will drop temporarily each time you add something, so take care to do just a few at a time and keep your oil in the frying range or your rings will be greasy.
6. Remove with the strainer or slotted spoon and transfer to kitchen paper to drain briefly. Salt to taste.

Keep finished rings warm and crispy in an oven at 100°C while you finish off the batch. Apparently you can freeze them and reheat them in the oven, but we didn't leave any to test this theory.

For people reading this who don’t currently own a sourdough starter, here is a non-sourdough onion ring recipe to try.

A couple of additional points I feel duty bound to relate. I was a tad nervous about having boiling oil in my kitchen. I made sure the work area was clear, the cats were not around me, I checked the amount of oil recommended to use for the size pan I have and used no more to avoid spillage. I also used an infrared instant read thermometer to check that the oil wasn't getting too hot. Smoke points and flash points for oils vary. The generic サラダ油 salad oil (usually a mix of canola and soybean oil) is most frequently used for deep frying here in Japan and has a flash point of 360°C (680°F). 天ぷら油 tempura oil is usually a mix of sunflower and sesame oils and is listed on this site as igniting from around 360 – 380°C (680-716°F). Both of these are somewhat far from the up to 190°C (370°F) I was aiming to maintain, but drips of oil falling onto the flames can cause fires even when the main body of oil in the pan is at a safe temperature.

So point number one: be safe, use a thermostatically controlled electric fryer if possible, and check how much oil your pan permits for safe use (usually no more than a third full). Don’t over-heat the oil causing it to smoke, and if it starts to smoke, then stop and turn off the heat before it sets alight. Never throw water on boiling oil and don’t try to move a pan that is on fire. Old advice about damp tea-towels is no longer recommended in the UK, the official recommendation of the fire service in the event of a pan on fire is to turn the heat source off if it is safe to do so, then get out and stay out and call emergency services.

Electric deep fryers are available in Japan, but many people still use the traditional type of tempura pan I used, and hence the most common cause of kitchen fires in Japan is from cooking tempura. The official line on kitchen fires from many ward offices is still to use a wet towel to extinguish a fire, and there are things such as this fire extinguishing flower that you throw into the pot, other advice recommends using a lid to try to extinguish a fire. Though I hope you'll never need it, the fire service number in Japan is 119. Some useful info here on the US embassy's site about calling emergency services in Japan.

Secondly: be a mensch, don’t pour the used oil down the drain. The oil will solidify and can block drains and sewage pipes. In Tokyo we are advised by our ward office to let the oil cool and pour it into a container such as an old milk carton that has scrunched up newspaper or fabric inside it, then tape the carton shut and put it in with your burnable rubbish. You can also get an oil coagulant which allows you to put the oil in solid chunks straight into the burnable rubbish.

You can use your oil a few times for frying, particularly if you strain it each time. But the oil will eventually become rancid with use and exposure to air. (Though apparently, the frequently retold rumour that repeated use of cooking oil produces of trans fats is untrue as long as the oil was not partially hydrogenated to start with. If you want to check the Japanese label of your oil, partially hydrogenated in Japanese is 部分水素化 bubun suisoka).

I've read on Japanese forums discussing tempura that using oil 3-4 times is a pretty good rule of thumb, but it depends on what you fry. If the oil becomes dark and starts to smell bad then it’s certainly time to throw it away.

Phew I had no idea when I started this post that it would turn into such a mammoth investigation of frying! Goodness me. Enjoy!