Start by rinsing the sushi rice under cold water in a fine mesh strainer. This is crucial for removing excess starch.
In a medium-sized pot, combine the rinsed sushi rice and water. Bring to a boil, then simmer covered for 18 to 20 minutes.
After cooking, remove from heat and let it sit covered for 10 minutes.
Mix together rice vinegar, sugar, and salt in a small bowl while the rice cooks.
Transfer the rice to a bowl, drizzle the vinegar mixture over it, and gently fold to mix.
Let the rice cool to room temperature.
Toast sesame seeds in a pan over low heat until fragrant.
Crush sheets of nori in a food processor and mix in toasted sesame seeds with salt.
Prepare the salmon, cream cheese, avocado, and cucumber by cutting into batons.
Lay a piece of nori on a bamboo mat, spread with sushi rice, then lay the fillings on top.
Roll tightly, slice into pieces, and arrange them to form a Christmas tree.
