Rinse the rice under cold water until the water runs clear.
Cook the rice in a rice cooker or pot with water according to package instructions.
Once cooked, let it sit for 5 minutes, then gently fluff with a fork. Mix in salt and rice vinegar (if using).
Heat sesame oil in a pan over medium heat. Add garlic and ginger, sauté for 30 seconds.
Add shredded chicken, soy sauce, and mirin. Stir-fry for 3-4 minutes until well-coated.
Mix in green onions, then remove from heat and let cool slightly.
Wet your hands lightly with water (or salt water to prevent sticking).
Take a handful of rice (~1/3 cup) and flatten it in your palm.
Place 1-2 tbsp of chicken filling in the center, then cup the rice around it, shaping into a triangle or ball.
Wrap with a strip of nori (optional) or sprinkle with sesame seeds.
Enjoy immediately or wrap in plastic wrap for later. Best eaten within a day for optimal texture.
