In a small pot over medium heat, add the rice vinegar, sugar, and salt and whisk to combine. Bring to a boil and continue whisking until the salt and sugar have dissolved. Remove the pot from the heat.
2. Step
Add the cooked sushi rice to a large bowl and the cooked black rice to a separate medium bowl. Add ¾ of the rice vinegar mixture to the sushi rice and the remaining ¼ to the forbidden rice. Mix until the vinegar mixture is well distributed.
3. Step
Make the shiitake veggie roll: Heat the sesame oil in a medium pan over medium heat. Once the oil is simmering, add the shiitake mushrooms, soy sauce, garlic powder, and pepper and cook for 6-8 minutes, until the mushrooms have released their juices and begin to crisp up.
4. Step
Place 1 sheet of nori over a bamboo sushi mat. Scoop 1 cup (230 g) of sushi rice on top of the nori. Fill a small bowl with water to dip your fingers into--this will prevent them from getting sticky when handling the rice. Using your fingers, spread the rice in an even layer over the nori, leaving a 1-inch (2-cm) border at the top to seal the roll.
5. Step
Over the bottom quarter of the nori, layer the spinach, cucumber, carrot, and shiitake mushrooms. Use your fingers to hold the vegetables in place while you begin to roll the nori. Squeeze the bamboo mat around the roll as you go to ensure a tight sushi roll. Transfer the sushi roll to a cutting board and cut it in half, then cut each half into quarters for a total of 8 sushi pieces.
6. Step
Make the sweet potato tempura roll: Heat the vegetable oil in a medium pot until it reaches 375ºF (190ºC).
7. Step
In a medium bowl, combine the flour, baking powder, salt, and pepper and mix well with a fork. Pour in the ice water and mix until incorporated--some lumps are okay. Drop the sweet potato sticks into the batter and toss with your fingers to ensure they are thoroughly coated.
8. Step
Transfer a few of the sweet potato sticks at a time to a spider and carefully drop them into the hot oil. Cook for 3-4 minutes, until crispy, then transfer to a paper towel-lined plate.
9. Step
Place 1 sheet of nori over a bamboo sushi mat. Scoop 1 cup (230 g) of sushi rice on top of the nori. Using your fingers, spread the rice in an even layer over the nori, leaving a 1-inch (2-cm) border at the top to seal the roll.
10. Step
Over the bottom quarter of the nori, layer the sweet potato tempura and avocado. Use your fingers to hold the vegetables in place while you begin to roll the nori. Squeeze the bamboo mat around the roll as you go to ensure a tight sushi roll. Transfer the sushi roll to a cutting board and cut it in half, then cut each half into quarters for a total of 8 sushi pieces.
11. Step
Make the avocado cucumber mango roll: Place 1 sheet of nori over a bamboo sushi mat. Scoop the forbidden rice on top of the nori. Using your fingers, spread the rice in an even layer over the nori, leaving a 1-inch (2-cm) border at the top to seal the roll.
12. Step
Over the bottom quarter of the nori, layer the avocado, cucumber, and mango. Use your fingers to hold the filling in place while you begin to roll the nori. Squeeze the bamboo mat around the roll as you go to ensure a tight sushi roll. Transfer the sushi roll to a cutting board and cut it in half, then cut each half into quarters for a total of 8 sushi pieces.
13. Step
Make the teriyaki tofu roll: Place 1 sheet of nori over a bamboo sushi mat. Scoop the remaining cup of sushi rice on top of the nori. Using your fingers, spread the rice in an even layer over the nori, leaving a 1-inch (2-cm) border at the top to seal the roll.
14. Step
Over the bottom quarter of the roll, layer the teriyaki tofu, red bell pepper, and carrot. Use your fingers to hold the filling in place while you begin to roll the nori. Squeeze the bamboo mat around the roll as you go to ensure a tight sushi roll. Transfer the sushi roll to a cutting board and cut it in half, then cut each half into quarters for a total of 8 sushi pieces.
15. Step
Serve the sushi with wasabi, pickled ginger, and soy sauce.
