Sushi Rolls (Maki Sushi - Hosomaki)

Bahan-bahan (10 porsi)

• 2¼ cups uncooked Japanese short-grain white rice
• 2¼ cups water ((for cooking the rice))
• 1 piece kombu (dried kelp)
• ⅓ cup rice vinegar (unseasoned)
• 3 Tbsp sugar ((skip if using bottled sushi vinegar))
• 1½ tsp Diamond Crystal kosher salt ((skip if using bottled sushi vinegar))
• 5 sheets nori seaweed
• 1 Japanese or Persian cucumber ((yields 8 rolls))
• 7 oz sashimi-grade tuna ((block; yields 12 rolls))
• 1 box natto (fermented soybean) ((yields 2 rolls))
• ¼ cup water
• 2 tsp rice vinegar (unseasoned)
• soy sauce
• wasabi ((optional))
• sushi ginger (gari) ((optional; you can make my homemade Sushi Ginger))