Make Sushi Rice by following the package directions. Including rinsing, soaking, and cooking- I cooked sushi rice and water in a 1:1 ratio in a rice cooker.
Add the hot cooked rice to a large bowl and toss with the vinegar, sugar, and salt. Allow to cool.
Bring half a pot of water to a boil and then lower to a simmer. Use a steamer basket to steam the tempeh for 15 minutes. Add steamed tempeh to a bowl and let cool until you can crumble the tempeh in to small pieces with clean hands.
Whisk together the vegan mayo, lemon juice, sesame oil, chili sauce, and salt and pepper to taste. Add the mayo mixture to the crumbled tempeh and mix well until coated evenly in the sauce. Taste and adjust salt and pepper to your taste.
Prep the avocado by slicing it into thin slices. If using other veggies, prepare those now.
Place your sheet of nori, rough side up, on a sushi mat. Keep a small bowl of water close by to dip your fingers in so the rice won't stick to you. Spread out the rice onto the nori sheet (see photo) and then add the spicy tempeh and avocado in a straight line on the side closest to you. Roll the sushi by lifting the nori over the filling tightly and then continue rolling while using the sushi mat to keep it tight. Use a sharp knife to slice your sushi rolls into 8 pieces.
Now, let's make the crunchy topping: Whisk together the vegan mayo and chili sauce to a small bowl. Taste and add more heat if desired.
Toast the panko breadcrumbs on medium heat until golden and crispy.
Dip the top of each piece of sushi into the spicy mayo and then directly into the toasted panko until all have been dipped. Top with sesame seeds and green onion if desired and serve.