Japanese Egg Sandwich (Tamago Sando)

Bahan-bahan (2 porsi)

• 3 large eggs (50 g w/o shell)
• ¼ tsp sugar
• ¼ tsp Diamond Crystal kosher salt
• ⅛ tsp freshly ground black pepper
• 2 tsp milk
• 2 Tbsp Japanese Kewpie mayonnaise
• 4 slices shokupan (Japanese milk bread)
• salted butter