There is a science behind this art form. Each ingredient, Asano says, needs to be cooked at a specific temperature and duration. When the perfect combination of these factors is achieved, only the batter would be deep fried to a crisp while the ingredients are steamed within the thin shell of flour, ensuring that their natural flavors are preserved.

Culture also plays a part in determining these factors.

"I try to cook just a little longer for Chinese diners. For example, some tempura chefs in Japan may cook seafood like squid, shrimp and abalone for one minute, but I'll cook them for an extra 20 to 30 seconds. Many Chinese people don't like it when the inside is not thoroughly cooked," he explains.

The oil and batter also make a difference. Because Japan-produced oils cannot be exported to China, Asano has resorted to using a special oil that features a blend of cotton seed, sesame and corn varieties. The batter is never premade and stored but prepared upon demand. To ensure crispiness, the bowl of batter is always nestled in a container of ice.