Preheat your oven to 400° F. Grab a scissor and cut your nori sheets into 4 equal squares.
Shrimp:
Slice your shrimp into small cubes and sprinkle with the tapioca flour. Toss to coat. In a medium bowl, mix the rest of the ingredients and then add the shrimp in to coat. Set aside.
Assembly:
To the center of a nori sheet, add 1 heaping tablespoon of rice and spread out slightly. Transfer the square to your muffin slot and use a spoon to press down gently, to center the rice in the middle with the edges coming up along sides of the muffin slot. Repeat in all twelve slots. Pop into oven for 5 minutes then remove. Top rice with about 5-6 pieces of shrimp to fill each slot. Transfer to your oven and bake for 10 more minutes.
Remove from the oven allow to cool slightly and top with your avocado, spicy mayo and black sesame seeds.
Notes
You can leave out the tapioca flour and they will still taste great. I recommend using a metal muffin tray.I also recommend using a melon baller or ice cream scooper to handle the sticky sushi rice.