• 2 cups all-purpose flour
• 1/2 tsp. baking powder
• 1/4 tsp. salt
• 1/2 cup (1 stick) unsalted butter , room temperature
• 1 cup sugar
• 1 large egg
• 1 tsp. pure vanilla extract
• Royal icing (recipe follows)
• 1/4 cup white and blue sanding sugar
• Blue food coloring , optional

• 5 Tbsp. meringue powder
• 1 pound (about 4 cups) confectioners' sugar

To make cookies: In a large bowl, sift together flour, baking powder and salt. With electric mixer, cream butter and sugar until fluffy. Beat in egg and vanilla.

Add flour mixture; mix on low speed to combine. Wrap in plastic and chill 1 hour.

Heat oven to 325°. On a lightly floured surface, roll dough 1/8-inch thick. Cut into fish shapes, 1 to 3 inches long, using a paring knife or cookie cutter. Transfer to ungreased baking sheets, chill until firm, about 30 minutes. Bake 10 to 12 minutes, until edges just begin to brown. Cool on wire racks; decorate with royal icing, some tinted blue if desired, and sanding sugar.

To make icing: Beat meringue powder and scant 1/2 cup water in electric mixer on low. Add confectioners' sugar, scrape sides, and beat until soft peaks form, about 10 minutes. To thin icing for filling in shapes, or "flooding," add a little more water.