Whisk together the mayonnaise, wasabi and sesame oil in a small bowl, and paint the tortilla wrap with this mixture on 1 side. Arrange a row of carrots horizontally 3/4-inch to 1 1/4-inch up from the bottom of the wrap you have in front of you. Then arrange the cucumber on top of the carrot in the same way, or as best as you can as it may slip down a little. Finally, top with the slices of tuna also lying them horizontally as this makes it easy to wrap up. Roll up the wrap as tightly as you can, starting from the bottom. You want to end up with a fat Cuban cigar. Cut across the rolled wrap diagonally to make 3 pieces.
Put the crabmeat into a bowl and add the mayonnaise, wasabi paste and oil and stir to mix. Lay the wrap in front of you and put the crabmeat in a line horizontally 2cm/about an inch up from the bottom of the wrap. Take the avocado half still with skin and scoop out the flesh in half teaspoonful curls, laying these on top of the line of crabmeat. Sprinkle over the lettuce in a neat line also, and then spritz with the lemon juice. Roll up tightly from the bottom, to form a fat cigar and then slice on an angle into 3 pieces. The 2 recipes combined make 6 pieces
Recipe courtesy of Nigella Lawson(Copyright 2007, Nigella Express, Hyperion, All Rights Reserved)