Stir the mayonnaise, the seasame oil and chili sauce in a bowl.
Dice the raw tuna and stir it in carefully with the sauce.
Cut the two sheets of nori in half.
Cover the sushi mat in plastic wrap to make it easier to roll the sushi.
Scoop out a small handful of sushi rice.
Place the rice on the sushi mat and gently spread it out.
Take a sheet of nori and place it on top of the rice on the sushi mat with the rough side facing up.
Add the tuna mix, avocado slices and the optional cream cheese, arranging them in a line along the width of the nori and rice
Roll the rice and nori up and over the tuna mix, avocado slices and cream cheese into a tightly packed cylinder, using the sushi mat.
Pull the sushi mat away gently and contiue rolling the nori and rice in the plastic wrap until the sushi is completely rolled. Use the mat to form it if needed.
Wet a sharp knife and slice the roll, wiping and re-wetting the knife to make it easier to slice uniformly.
Gently pull the plastic wrap away from the sliced sushi rolls and sprinkle black sesame seeds on top.
Serve with wasabi, soy sauce and ginger as garnish, eat immediately- the raw fish will not store well in the refrigerator.
