Mix the smoked trout, avocado cubes and cream cheese in a bowl together. Set aside.
To halve a nori sheet, place it in front of you with the lines running vertically. Hold the top of the nori sheet and fold it in half. Gently press on the sheet and then it should easily pull apart into two halves.
Lay half a sheet of nori shiny side down. Place the water bowl and damp cloth nearby. Put a heaped tablespoon (60g) of sushi rice on the left side of the nori sheet. Use moistened fingertips (using the water bowl) to spread the rice evenly over nearly half of the nori sheet. Use the water bowl and damp cloth to remove rice from your fingers.
Place a few lettuce leaves at a 45-degree angle on the rice. Then carefully place some of the smoked trout mix on top of the lettuce (try not to overload with ingredients as this will make it difficult to roll).
Carefully roll the temaki by folding the bottom left corner of the nori towards the top right corner of the rice. Continue to fold and place a few grains of cooked rice on the final corner of the nori to complete and hold the fold.
Fill the temaki with another spoonful of the smoked trout mix. Garnish with a spoonful of caviar or mixed sesame seeds. Make seven more temaki rolls in the same way.