Sandwich tuna

Bahan-bahan (4 porsi)

• 425 g / 15 oz canned tuna in oil (, drained (Note 1))
• 3/4 cup whole egg mayonnaise or Kewpie ((Note 2))
• 3/4 cup finely diced celery ((1 stalk, cut in 4 lengthways, then finely diced))
• 5 tbsp finely chopped dill pickle ((Note 3))
• 2 tbsp liquid from pickle jar ((Note 3))
• 2 tbsp Dijon mustard
• 3 tbsp finely chopped dill ((or parsley or basil))
• 1/3 cup finely sliced green onion (, ~2 stems (Note 4))
• 1/2 tsp black pepper
• 8 pieces butter lettuce ((2 per sandwich))
• Salted butter (, for spreading)
• 8 slices bread or 4 rolls ((Note 5))