In a small saucepan, combine cornstarch and water until smooth. Bring to a boil over medium heat. Cook and stir for 2 minutes or until thickened. Refrigerate for 1 hour.
In a large bowl, cream butter and sugar until light and fluffy. Beat in almond extract. Add cornstarch mixture and beat until sugar is dissolved and frosting is fluffy, about 4 minutes. Store in the refrigerator.