Onigirazu is the cool new rice sandwich

Over the summer in Japan, the big food craze was a stuffed, roasted seaweed and rice sandwich called onigirazu.

It's not, however, completely new - this sandwich is an expansion on the traditional onigiri, those often adorable compact rice balls that Japanese mothers make for their children's bento lunches. Onigiri are usually big enough for one or two bites and contain small pieces of preserved plum or fish in the centre. The outside is rolled in seeds or furikake (rice seasoning) or wrapped in a strip of dried seaweed.

Onigirazu are larger and with more fillings. First, a square of roasted seaweed is topped with warm cooked seasoned sushi rice. Then the filling is laid on top. Leftover cooked meat, cold cuts or stir-fries are often used, along with lettuce or cucumber and tomato slices, as well as mayonnaise and ketchup - just like in a sandwich made with bread. After that, more rice is scooped on top of the filling before the seaweed to wrapped around it like a parcel, then in cling film, and left for a few minutes to soften. The parcel is then cut in half to reveal the layers of fillings.

I've read that there's a special kind of nori sheet for onigirazu, which is bigger and thicker than the type for sushi rolls or onigiri. The ones that we can easily get here seem to work fine, but if they keep splitting, use two pieces of seaweed instead of one. Or don't stuff too much into the sandwich!

In my bento lunch, the filling for the onigirazu is battered chicken strips in a hot sweet sauce. Along with it in the bento box are braised lotus root, and tofu and broccoli stir-fry, all cooked Japanese style. For dessert, there's Japanese red bean pancakes or doraki.

Watch the short video above to see how to assemble onigirazu. Use sushi rice, and cook and season it according to the packet instructions. Use fillings that do not have too much liquid or gravy. This sandwich can take quite a lot of filling because the rice is compressed; still, remember not to overfill.

The cling film can be removed once the onigirazu is "set". My personal preference is to leave the cling film on when I pack my lunch and remove it just before eating.