Sushi rice is cooked white rice seasoned with su, or seasoned, sweet vinegar. To make good sushi, whether maki (rolls) or nigiri (sushi made by gripping) the rice must have the correct texture: fluffy and moist. If it is too sticky, too mushy, too firm, over or under-seasoned, the sushi will be an abysmal failure.
Perfect sushi rice does not have to be difficult to prepare but there are key techniques to keep in mind. Sushi rice must be made with medium or short-grain Japanese (Japonica) polished white rice. If you do not have any, wait until you do. Other rice varieties lack sufficient stickiness to hold together. There are various brands of Japanese white rice. Choose the best quality rice possible for your sushi. Some inexpensive brands mix in broken grains with whole grains. Others are medium grain, which while suitable enough, are substandard compared to super premium short grain varieties that the Japanese prize, such as Hoshi Hikari or Akitakomachi. (Secret #1: A lesser known fact is that the new crops of rice are less suitable for sushi as the younger grains do not absorb the su as well as rice that has been stored for a few months.)
I am surprised that sushi rice recipes vary so greatly. In my humble opinion, it is good to exercise creative license with your own recipes but it also is good to pass on traditional recipes as well. Sushi rice, for example, never uses soy sauce. (And Chef Robert Irvine, I think you are terrific but miso paste in sushi su?!) Sushi shops have their own secret techniques and recipes, but here are the basics:
Measure and wash rice (gohan)
Once, Japanese white rice was polished with powdered talc to give the grains an attractive appearance. This practice is on the decline due to the reported cancer risks related to talc. Nevertheless, it is good to wash thoroughly rice manufactured overseas. In the US, some rice is vitamin-enriched, in which case, it is best not to wash it too vigorously or the nutrients will go down the drain.
Measure three level cups of rice, using a standard measuring cup, into a rice pot. Japanese measuring cups use the metric system and are smaller than US cups but as long as you use the same measuring implement for both the rice and the water, the result will be fine. Pour in running water and squish the rice in the water with your hand. Drain then repeat until the water runs clear. Drain rice well.
Carefully measure three cups of fresh water into the pot with rice. Cover with the lid and allow it to soak for about 30 minutes. This allows the rice grains to soften slightly without getting water-logged. Soak it too long and the cooked rice will be too mushy for sushi. (Secret #2: If you prefer heavily flavored sushi rice and plan to add more su, then subtract one tablespoon of water for each cup of rice before cooking. This way, the cooked rice will absorb more su.)
Make the su
In a small pot, heat the rice vinegar and sugar, stirring to dissolve. Let the mixture cool. Sushi chefs use their own ratios of rice vinegar to sugar. Some use as little as 4 Tbsp. of rice vinegar with 1 Tbsp. of sugar for three cups of rice. The rice virtually has little su flavor at all. At the opposite end, Hawaii-style sushi chefs use as much as a 50:50 ratio of rice vinegar to sugar with 1/4 cup of su for every cup of rice. A good standard Japan recipe is:
3/4 cup rice vinegar (regular type. Do NOT get lite or seasoned)
2 Tbsp. sugar
1 Tbsp. mirin, optional (*most sushi chefs add either mirin or sake)
Cook the rice
Use an electric rice cooker for convenience. Although some high-end Japan establishments retain the tradition of cooking gohan in a kama (heavy pot) over an open flame, even some of the best sushi restaurants use technology to their advantage. But if you are set on cooking rice the old fashioned way, then place the pot (thick bottomed pot) over a medium flame and bring the contents to a boil. Cover with a tight-fitting lid, lower the flame to low and let the rice cook for about 15 minutes. Do not lift the lid! Turn off heat and steam for an additional 15 minutes.
Fan the rice
Wet a large hangiri/sushi-oke/handai (wooden bowl). Drain out water. Using a wet shamoji (rice paddle) or wooden spoon, pour in the cooked rice without breaking the rice grains. Wetting the utensil will keep rice from sticking to it. Fan the rice with a hand fan. (Secret #3: This is said to keep the grains glossy.) You also want the water to evaporate out of the grains so the rice will absorb the su. (My Secret #4: Because I cannot seem to master fanning while carefully turning the rice with a shamoji, I use a small electric fan placed on my work space and set on low.)
Lightly salt the rice with about two teaspoons of fine sea salt, not coarse grain, and continue to turn the rice with the shamoji for about five minutes, if using an electric fan. Ten minutes if using a hand fan. Rice should be warm. (Secret #5: If the rice is too cool, it will not absorb the su well. If it is too hot, the su will evaporate when it comes in contact with the steaming hot rice.)
Combine the rice with the su
Again, sushi chefs differ. Some use little su. Others flavor their rice more heavily. A good starting point for lightly flavored Japan sushi is to add 2 or 3 Tbsp. of su for every cup of rice. Carefully turn the rice until the su is absorbed. (Secret #6: If you prefer your rice more seasoned, add more su but be sure each addition is completely absorbed before adding more.)
The sushi meshi, or prepared sushi rice, is ready for rolling, pressing or wrapping as desired. (Final Secret #7: Keep the sushi rice slightly warm but not hot, about body temperature. Cold sushi rice does not roll or press well.)
Shhh, now you know sushi chef secrets.