Combine cornstarch, Splenda, and sugar in a small sauce pan.Add milk slowly, stirring to prevent clumps.Cook mixture over medium heat until boiling.Cook and continue to stir for at least 1 minute until thickened.Stir in chocolate chips.Continue cooking and stirring until chocolate is melted.Remove saucepan from heat and stir in vanilla.Place in serving bowls and chill until set.