(Before you begin, prepare the cucumber by skinning it with a cheese knife or grater.) Hold the cucumber in one hand, and with your chopping knife, line up the blade almost vertically to the cucumber. Without exerting too much pressure, start to slice around the circumference of the cucumber as if you were skinning an apple. Bring the knife downward towards you as you slice, then upwards again as your knife moves across the flesh. Be sure not to angle the blade too much or you’ll end up with cucumber sheet that is thicker in some parts than others.
To give you an idea of the approximate thickness, when cutting, you should just be able to just see the blade of the knife through through the cucumber flesh. About 1/4 of a centimeter (1/10 of an inch) in thickness should suffice.
Tip: Dip the blade of your knife into the bowl of water every once in a while to help it glide through the cucumber flesh more easily.
Cut the tuna into thin slices using a moistened chopping knife. Start each cut by lining up the heel of the knife with the corner of the tuna closest to you. Allow the knife to glide as you pull it through in one fluid motion, ending the cut at the knife tip. Slices should be approx 1/4 cm (1/10 of an inch) in thickness.
Starting at one end of your cucumber sheet, layer on your pieces of tuna, leaving 1cm at the end for rolling. The tuna should cover approximately one third of the entire sheet. Add a line of three avocado slices on top of the tuna, somewhere close to the middle.
Using your finger, add a dab of wasabi in a straight line next to the avocado slices.
Then, using your fingers, roll the cucumber sheet – remembering to compress slightly to help contents pack together. Keep rolling until there is just a small section of the sheet left. Here, you can add a little mayonnaise, mascarpone cheese or natural yogurt to act as an adhesive for your roll and help it stick together.
When cutting your sushi roll, make sure the seal line is at the bottom so that it doesn’t unfurl as you slice it into segments.
Cut off both ends of the roll first and discard.
Cut the roll into 1 cm segments. Remember to keep motion of the knife fluid. Use a single through movement of the knife to slice each segment and avoid ragged edges.
Place four segments face-down onto a decorative plate with equal space between each. (Imagine each being the marker for each corner of a square).
Arrange a small handful of shredded daikon at the center of the square. Top with a pinch of shredded carrot to give it some color, and some green salad or rocket leaves.
Next, layer a generous tablespoon of salmon roe onto each of your cucumber roll segments.
For added contrast, drizzle a small amount of soy sauce onto the plate, allowing it to pool naturally around the cucumber roll segments.