1) In the container of an electric blender, put half of the ice cream and half of the lemonade concentrate. Blend till the mixture is smooth.
2) Pour mixture into tart shells.
3) Repeat procedure with the remaining lemonade concentrate and ice cream.
4) Freeze till the mixture has firmed.
5) About 5 minutes before serving, remove the filled crusts from the tart pans carefully and serve chilled. If desired, top with chocolate shavings.