1/2 tsp cornstarch, dissolved in 1 1/2 tsp cold water
6–8 flowering chives or toasted nori, cut into thin strips
black and white sesame seeds
Place the rice and water in a rice cooker set to the sushi rice setting. Once the rice is done, stir in the sesame seeds, rice vinegar, sugar and salt and allow to slightly cool.
Place the sesame oil in a small pan (preferably cast iron) over medium heat. Trim a little off the edges of the shiitake caps to make all of the caps uniform in size if you want. Add in the shiitake caps, gill side down, for about a minute. Flip them over and drizzle the 1 TB of water over the top, and allow to soften for about a minute more. Dab off any remaining moisture with a papertowel.
Add the Everything Sauce over the shiitake, then flip again. Drizzle the cornstarch/water mixture over the top, stirring immediately. Once it thickens, remove the pan from the heat and set aside to slightly cool.
To form the nigiri, separate the cooled rice into 6-8 equally sized, football-shaped pieces (wet your hands first to prevent sticking). Drag the shiitake through the sauce, then place on top of the rice.
If using flowering chives, run them under hot water for about a minute to make them pliable. Tie the chive securely around the nigiri, or or wrap a toasted nori strip around it, using a bit of water to seal it. Sprinkle with extra sesame seeds, then serve immediately with soy sauce.