Rice:
I use a rice cooker. Combine the water and rice and cook per the instructions on your rice cooker. If you don’t have a rice cooker, you can try these instructions (I’ve not done them myself): Wash, drain, and soak the rice in water for at least 30 minutes, then drain. Combine the rice and measured water in a saucepan and cover. Place the pan over moderately high heat. When the water boils, reduce the heat and cook for about 10 minutes. Turn off the heat and allow the rice to steam undisturbed for at least 10 minutes (don’t remove the lid or you’ll ruin it).

Dressing:
Combine the vinegar, salt, and sugar in a bowl and stir until salt and sugar are dissolved.

Sushi Rice: Wet a mixing bowl large enough for the rice. Wipe off excess water. Wet the tub a second time with vinegared water (1 cup water + 2-3 tablespoons vinegar). Wipe off any excess. Heap the cooked rice in center. Allow rice to cool in the tub for 10 minutes. Pour the dressing over the rice and mix the dressing evenly with a large spoon or rice paddle. While mixing, fan the rice to cool it. The rice is ready to use when it reaches body temperature.

spicy tuna
1 lb. maguro (sashimi-grade tuna), coarsely chopped (yields about 2 cups) 1/4 cup mayonnaise (to taste)
sriracha sauce (to taste)
Mix a tablespoon of mayonnaise at a time into the tuna until it reaches the consistency you prefer. Mix in a little sriracha at a time until you get the desired spiciness.

crab salad
1 cup crab meat (cooked) or surimi (aka krab), shredded by hand (nothing fancy) 1-2 tbsps mayonnaise (to taste)
Mix a tablespoon of mayonnaise at a time into the crab meat until you get the desired consistency.

Volcano roll: Divide the cup of mayonnaise into two half-cup quantities in separate bowls. Mix a teaspoon of water into the wasabi powder and stir until the water is absorbed. Continue adding a little bit of water and stirring the wasabi until you achieve a nice paste (you can make it pretty dry or more wet as you like – the less dry it is, the more easily it will mix into the mayonnaise). Add a teaspoon of wasabi paste to a half cup of mayonnaise and stir until combined. Press out any lumps. Add more wasabi until the mayonnaise is spicy enough to your liking. Now add sriracha by little squirts to the remaining half cup of mayonnaise and stir until uniform. Taste for spiciness and adjust accordingly. If you overdo it on either of the mayonnaises, just add more mayonnaise to cut the heat. Place each mayonnaise in a squeeze bottle.
On a sheet of plastic wrap, set down one sheet of nori. With wet hands, grab a handful of sushi rice and evenly spread across the top 3/5 of the nori sheet, pressing the rice down to ensure it sticks to the seaweed. Flip the nori over so that the rice faces down onto the plastic wrap. At the non-rice end of the nori, lay out a dozen cucumber strips parallel to the edge of nori with an inch of margin. Layer 2-3 avocado slices on the cucumber, then spread a quarter of the crab salad over the avocado. While it is tempting, don’t overfill the roll. Roll the fillings up from the non-rice end of the nori (like a carpet) and continue to roll tightly, but not too tightly until the rice encompasses the entire outer part of the roll. Use the plastic wrap to help maintain shape without letting the roll stick to you. Use a bamboo mat to firm up the shape (round – we’re shooting for round) and compact the roll. Remove the bamboo mat and the plastic wrap from the roll.
At this point you can either pile spicy tuna on top of the roll and lay the plastic wrap over it and around the roll for ease of cutting (this is faster, me thinks) or cut the roll without any tuna on it and put the tuna on the individual cut pieces. If you choose the first method, use a really sharp knife, dip it in water, and slice the roll in half through the plastic. Cut the two remaining pieces in halves and repeat again until you have 8 pieces. A sharp knife is important or else you’ll just squash all of your hard work. When the roll is cut, peel the plastic off – it should come off in one shredded piece, but nothing should be left on the roll. If you choose the second method (no tuna on top) dip a very sharp knife in water and cut the roll in half. Repeat until you have 8 pieces. Arrange your non-tuna pieces on a plate and carefully spoon spicy tuna onto each piece.
Top the tuna with masago or tobiko, then squeeze some sriracha mayonnaise over the roll, followed by a squeeze of wasabi mayonnaise. Sprinkle with black sesame seeds. Serve with wasabi, gari (pickled ginger), and soy sauce. This makes at least 4 cut rolls.