Sandwich ayam

Bahan-bahan (10 porsi)

• 500 g / 1 lb cooked chicken meat from 1 large store bought roast chicken ((Note 1))
• 1 celery stem (, sliced 3mm/0.1" thick then into 0.5cm/0.2" pieces)
• 1 g reen onion stem (, finely sliced)
• 3/4 cup walnuts (, roughly chopped (Note 2))
• 3 tbsp finely chopped cornichon/dill pickle
• 1 1/2 tbsp finely chopped dill ((Note 3))
• 2/3 cup whole egg mayonnaise ((S&W best in Aus, Note 4))
• 2/3 cup sour cream ((sub full fat yogurt))
• 2 tsp Dijon mustard
• 1 1/2 tbsp lemon juice ((sub white wine or cider vinegar))
• 1/2 tsp onion powder ((or more garlic powder))
• 1/4 tsp garlic powder ((or more onion powder))
• 3/4 tsp cooking/kosher salt
• 1/4 tsp black pepper
• Salted butter (, for spreading on bread)
• 20 slices white sandwich bread, day-old, ((or more slices for less filling) (Note 5))