Begin by coating your bamboo mat in plastic wrap and placing it on the table in front of you so that the bamboo runs lengthwise and you can roll the mat away from you. Lay your nori down on the mat and coat it in sushi rice, keeping your fingertips wet as you work with it.
Once the nori is coated in rice, flip the sheet over. With the nori side up, place your surimi, cucumber, and avocado at the top of the sheet, running lengthwise like the bamboo.
Beginning at the top with your fillings, roll the mat towards you until the edge of the mat meets itself. Lightly squeeze your roll in place to make it as tight as possible without bursting open. Carefully peel back the end of the mat so you can continue rolling your sushi roll without rolling the mat into it.
Cut your roll into pieces roughly 1 ½" - 2" wide using a very sharp knife. Run the blade under lukewarm water before cutting.
Top each piece with smoked salmon, sesame seeds, and chives.
Serve with soy sauce, wasabi, pickled ginger, and enjoy :)
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Notes
The most important thing to remember when making sushi is that anything that touches the rice should be wet. Sushi rice is sticky, so it will stick to anything it feels, creating an even bigger and bigger mess anytime it gets touched. This is often the most significant challenge home chefs have with making sushi. Keeping your fingers wet as you work with the rice will allow you to maneuver it without it sticking to your hands.
When slicing your sushi, use the sharpest, non-serrated knife you have, as a dull knife can crush the roll, ruining all your hard work. Wet the blade with some lukewarm water to stop the sushi rice from sticking to the knife, and confidently slice into the roll. Wipe the edge off, and rinse it with water between each slice to keep your cuts clean.