This is a recipe for adorable fish-shaped butter sandwich cookies. Using room temperature butter as a base, mix in powdered sugar, salt, beaten egg, cake flour, and skim milk powder to make the cookie dough and butter filling. After chilling both thoroughly in the refrigerator until firm, cut out the cookie dough with cookie cutters, and cut out a circle in the center of some of them. Sandwich the butter filling between the baked cookies and draw cute faces with melted chocolate to finish. When chilled, the harmony of the crispy cookie and rich cream is exquisite. It's easy enough for beginners to make and is perfect as a gift or for enjoying at home.