Start by preparing your avocados. To do so, remove the pit from the center of the avocado. Then use your hands to carefully peel the skin off of the outside of the avocado (without squishing the flesh of the fruit).
Once the avocado flesh is separated from the skin, place the avocado inside-down on a cutting board. Use a knife to thinly slice the avocado. Then, use the side of your large knife to very gently press on top of the avocado until the slices start to separate and the avocado lengthens.
When the avocado is about ½ - ⅔ the length of your sushi roll, pause. Set this aside.
Now begin rolling your sushi. Wrap your sushi mat in plastic wrap in order to keep it from getting dirty.
Place a half nori sheet on top of your sushi mat, shiny-side down.
In a small bowl, combine the ¼ cup water and 2 tsp rice vinegar for your hands. Whisk to combine.
Measure out ½ cup of sushi rice and place it on top of your nori sheet. Dip your hands in this vinegar water so that you can touch the rice without it sticking to your hands. Use your hands to spread the rice over the entire nori sheet.
Once the rice is spread out, flip the nori sheet over. Place 2 pieces of shrimp tempura at the bottom edge of the nori sheet. Place 1-2 strips of cucumber across the length of the nori sheet as well. Finally, sprinkle about 1 tsp of tobiko over the ingredients.
Place your thumbs under the sushi mat. Then lift the edge of the mat closest to your belly up and over the filling in the center.
Use your hands to press the length of the log, making sure that all of the sushi ingredients are staying together. Continue lifting and rolling the edge of the sushi mat until the sushi is in one roll. Gently press with your hands again to make sure that the rice on the outside edge is sticking together. If you need visual instructions for this process, I enjoyed watching this video.
Once the sushi is rolled, remove the sushi mat. Use the flat side of your knife to pick up the avocado slices and lay them across the top of your sushi roll. Place a piece of plastic wrap over top of the avocado. Then put the sushi mat over the top of the sushi roll and gently squeeze until the avocado slices match the shape of the sushi roll.
Remove the bamboo mat but keep the plastic wrap on top of your sushi roll. Use your knife to cut the sushi into 8 pieces through the plastic wrap. Once cut, remove the plastic wrap.
Place the cut sushi on your serving platter. To decorate, spoon a pinch of tobiko onto each piece of sushi. Then drizzle about 1 tsp of sriracha mayo over the top of the roll and a pinch or two of black sesame seeds. Place a few dollops of unagi sauce on your plate for dipping.
Repeat until all of the sushi rolls are ready. Serve and enjoy!