Beat the egg, fish sauce, soy sauce, caster sugar, lemon juice (or mirin) and a pinch of pepper in a small bowl or cup.

Add the vegetable oil to a small non-stick pan and place it over medium heat. Once the oil is warm, pour in the beaten egg.

Don’t stir the egg. After 1 minute, place a lid over the pan and turn the heat low. Let the egg set for 3 to 4 minutes until the surface is cooked through.

Then remove the omelet from the pan and let it cool on a clean plate. Place the nori on a clean chopping board. You can use a serving ring to assemble the sandwich or pile the ingredients neatly on top of each other. I use a serving ring (if you do too: using the serving ring, cut a circle out of the omelet first). Place half of the cooked rice on top of the nori. Shape it into a clean circle if you have no serving ring.

With a knife or a pair of scissors cut the omelet into the right shape to fit the rice and place it on top.

Divide the smoked salmon over the omelet covering it neatly.

Then add the lettuce.

And end with the rest oft he cooked rice. Make sure the sandwich is not too thick.

Then brush the sides of the nori with a little water and fold the corners to the middle.

Wrap the sandwich tightly in cling film.

Place the sandwich in the fridge for at least an hour. Slice it in half and serve.