Foryoueats: Tuna sandwich

Ingredients

• Tuna sandwich filling:
• 425g/ 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
• For sandwiches:
• 8 pieces butter lettuce (2 per sandwich)
• Salted butter , for spreading
• 8 slices bread or 4 rolls (Note 5)