– 1 cup unsalted butter – 2.5 cups powdered sugar – 2 small eggs – 1 ½ teaspoons vanilla extract – ½ teaspoon salt – ⅓ cup cornstarch – 3 ½ cups all-purpose flour – 2 ¼ Tablespoons water – 1 Tablespoon meringue powder – ¼ teaspoon clear flavor extract