Slowly bring dashi to a boil over medium-low heat then turn off heat.
Dissolve miso in the dashi. Add tofu, wakame, and scallions just before serving. (Do not boil after adding miso).
Rice
Wash and rinse the rice until the water is clear. Drain well. Cook according instructions on the package.
Season with rice wine vinegar. Cover with a damp cloth to prevent drying.
California Roll
Prepare the fillings: mix crabmeat and mayonnaise.
Cut cucumber and avocado into thin strips, squeezing lemon juice over avocado to prevent browning.
Roll the sushi: Cover bamboo sushi mat with plastic wrap.
Place a sheet of nori shiny side down on the mat. Wet fingers in water and spread sushi rice evenly on the nori.
Arrange crabmeat, cucumber, and avocado along the bottom edge of nori.
Roll sushi mat tightly, shaping into a cylinder. Cover rolls with a damp cloth.
Spicy Tuna Roll
Prepare the filling: Combine tuna, sriracha sauce, sesame oil, and scallions in a bowl.
Roll the sushi: Place a sheet of nori shiny side down on a bamboo mat covered with plastic wrap. Spread sushi rice evenly on nori and sprinkle with 1 TBSP sesame seeds.
Roll sushi mat tightly, shaping into a cylinder. Cover rolls with a damp cloth.
Make the spicy mayo: Combine all ingredients and whisk in a bowl.
Iced Matcha Latte
Make the simple syrup: Combine sugar and water in a small saucepan. Heat until sugar dissolves. Cool and store.
Make the iced matcha latte: Add ice cubes and milk to a tall glass.
Sweeten with simple syrup.
Whisk matcha with hot water until smooth and foamy. Pour into the glass. Stir well.
Finish and Serve the Meal:
Wet the blade of a sharp knife and cut each spicy tuna roll into 6 - 8 pieces. Clean the knife with a damp cloth every few cuts. Top the whole roll with spicy mayo or serve on the side.
Cut each California roll into 8 pieces using the same method.
Serve sushi rolls with an optional side of wasabi, pickled ginger, and a small dish of soy sauce for dipping. Enjoy with miso soup and an iced matcha latte.