To make the sushi rice, place the rice in a bowl and cover with water. Stir the rice using your fingers until the water turns a milky white colour. Drain in a colander and return the rice to the bowl. Repeat this washing and draining process four or five times, until the water is clear

At this point, place the rice in the bowl, cover with water and leave to soak for 20 minutes

Drain the rice and add to a pan with the 300ml of water and small piece of kombu. Place a lid on the pan and cook over a high heat for 5 minutes, then reduce the heat and cook for another 20 minutes

While the rice is cooking, make the sushi vinegar by placing all the ingredients in a small pan and heating until the sugar and salt have dissolved. Keep the vinegar warm

When the rice is cooked, place it in a mixing bowl. While it and the sushi vinegar are still hot, add the sushi vinegar to the rice, cutting into the rice using the side of the paddle to avoid breaking too many grains

When the vinegar is incorporated, transfer the rice to a plate or tray, top with a damp sheet of kitchen paper and set aside to cool

If your salmon still has the skin on, take the fillet and place skin-side down on a board. With your knife parallel to the board, slice away the skin of the salmon using smooth, sweeping motions, cutting about 5mm from the skin into the flesh. Discard the skin

Cut two long, 1cm thick slices along the fillet – you want them to be as long as a nori sheet is wide. Slice each in half again lengthways to give you four long pieces of salmon

Prepare the cucumber by cutting it to the size of your nori sheet. Cut into quarters and remove the seeds. Peel the avocado and cut the flesh into neat slices

Place the bamboo mat on a work surface and place a nori sheet on top, shiny-side down. Moisten your hands and take a large handful of rice weighing 180g–200g. Place the rice on the nori, leaving 3cm space at the top of the sheet. Gently spread out to cover the rest of the sheet

Place a slice of salmon in the centre, and the slice of cucumber next to it. Place some avocado slices on top of the salmon, and the other slice of salmon on top of the cucumber – you are now ready to roll

Using the bamboo mat, roll the nori and rice around the filling (working away from yourself), and use your fingers to keep the filling in place

Once completely rolled, gently but firmly shape the mat around the roll to create a nice cylindrical shape

Moisten your knife and make a cut in the centre of the roll. Each time you slice, wipe your knife with a damp cloth and moisten the knife again

Repeat with the remaining ingredients to make more futomaki. Carefully place the slices on a serving plate with wasabi paste and pickled ginger and serve