Chinese cuisine doesn't lack for expensive delicacies. Dried abalone, bird's nest and shark's fin are standards at Chinese banquets, but sometimes, exquisite foods require more than just the ability to hand over a platinum credit card. The coveted yellow oil crab (wong yau hai) is so rare - it's available for just a few months a year - that money won't guarantee a taste to the most pampered palates. These crabs aren't as famous as the Shanghainese hairy crabs eaten in winter and also prized for their roe, but they're certainly rarer. Wong yau hai are available only in the hottest months of summer. They're caught in shallow waters when the scorching heat of up to 40 degrees Celsius makes them frail and weak. The extreme heat melts the roe, transforming it into a flood of rich yellow oil that permeates the entire body of the crustacean to the tips of the claws. The melted yellow roe is the reason the crabs are so sought after by serious foodies. 'Once cooked, the fragrant yellow oil oozes out like ice cream,' says Chui Wai-kwan, proprietor of Fook Lam Moon Restaurant. 'It's creamy and soft in texture and has the yellowness of salted egg yolk.' The crabs are fussy creatures. In order for the roe-to-liquid transformation to occur, the weather can't be excessively wet, cold or hot, says Lau Wai-leung, Lei Garden's executive chef. He describes the ideal conditions as similar to a Swedish sauna. The supply of wild yellow oil crabs has dwindled rapidly in recent years due to water pollution and temperature fluctuations. Most yellow oil crabs are farmed, which has lengthened the period they're available. 'In the old days when people were eating mostly wild crab, the season would only last two to three weeks,' says Chui. 'But thanks to improvements in technology, yellow oil crab can now be eaten from June to August.' Connoisseurs say the measure of a superior yellow oil crab lies in the golden-yellow glow in the claws and limbs. The yellower the better because it's more likely a wild crab, which are considered sweeter than the farmed variety. The prices also reflect that difference. Wild specimens cost about HK$200 more per catty than their farmed counterparts, says Ma Kwai-ming, a chef at the Four Seasons Hotel's Lung King Heen Restaurant, which sources its wild yellow oil crab from Lau Fau Shan in the New Territories, where up to 80 per cent of the crabs sold have been farmed. 'The wild catch is increasingly hard to come by,' says Ma. 'You need to have close relationships with the suppliers in order to get the best quality.' There are huge price variations in the market, but like many other things, you get what you pay for. Good quality yellow oil crab averages about HK$400 per catty - which is between five and eight times more than regular crab. The rarity of the seafood means chefs have to treat it with care and respect. Most devotees say the best ways to taste the delicacy are to immerse it in Chinese wine, rendering it 'drunk', to bathe it in ice and rose water, or refrigerate it before steaming it. 'All the preparation work is part of an effort to keep the crab intact during cooking,' says Leung Chung-keun of the Dragon King Restaurant Group. 'There's a danger that the crabs move around in reaction to the hot steam, possibly breaking the claws and spilling the precious yellow oil, which would make the crab unusable and would be a huge cost for us to bear. After all, the yellow oil is what makes the crab valuable.' Aside from steaming, restaurants cook it in congee, braised shark's fin soup or Shanghai steamed soup dumplings (xiao long bao), but many eateries are wary about being too creative due to the expense. 'Given how expensive the crab is, it doesn't always make economic sense to use it in a dumpling, for example, because it would be hard to justify the cost,' says Bao wei-dai, manager of Fu Sing Shark Fin Seafood Restaurant, who advocates steaming or baking. Because of the crab's delicate nature, most restaurants are reluctant to keep stock, and advise customers to pre-order. Fook Lam Moon and Lung King Heen source the crabs only after an order has been placed. 'Unlike normal crabs, which can be kept alive in tanks over three to four days, the yellow oil crab is a different animal,' says Ma. 'They'll only survive one to two days because they're so frail. That's why we prefer not to keep any stock.'