In a medium saucepan, combine strawberries and sugar. Cook over medium heat until sugar is dissolved. Remove from heat and set aside.
In a small bowl, combine cornstarch and water, stirring to combine. Add cornstarch mixture to strawberry mixture. Return to stovetop and cook over medium heat for approximately 5 minutes, stirring frequently, until thickened and clear. Strain and discard seeds. Cover and refrigerate for 1 hour before using.