01 - Rinse the sushi rice thoroughly under cold water until the water runs clear. Combine rinsed rice and water in a small saucepan, bring to a boil, then cover and reduce heat to low. Simmer for 10 minutes, turn off the heat, and let stand covered for an additional 10 minutes.
02 - In a small bowl, whisk together rice vinegar, granulated sugar, and kosher salt. Gently fold the seasoning mixture into the warm rice with a spatula until evenly distributed. Allow the seasoned rice to cool to room temperature.
03 - Place a single sheet of nori, shiny side facing down, on a bamboo sushi rolling mat. With damp hands, spread a thin, even layer of cooled sushi rice over the nori, leaving a 1-inch border at the top edge.
04 - Evenly sprinkle black and white sesame seeds over the surface of the rice.
05 - Lay a row of each prepared filling—julienned bell peppers, cucumber, carrot, avocado, chopped pickled ginger, and cream cheese if using—across the bottom third of the rice layer.
06 - Using the bamboo mat, lift the edge of the nori and roll tightly, keeping the fillings in place. Seal the edge of the nori with a small amount of water to secure the roll.
07 - With a sharp, damp knife, slice each sushi roll into 4 evenly sized pieces for clean presentation.
08 - Arrange the cut rolls on a serving platter. Present with soy sauce or tamari, wasabi, and extra pickled ginger as desired.