Prepare and bake pie shell according to package directions for a baked pie shell. Set aside to cool.
Whisk egg yolks, sugar and flour in a medium bowl.
Heat milk and vanilla in saucepan until almost boiling. Remove from heat; add to egg mixture, 1/4 cup (50 mL) at a time whisking continuously, until all of milk has been added. Return custard to saucepan and cook over medium-low heat, whisking continuously, until custard has thickened to a consistency similar to pudding (5-7 minutes). Place plastic wrap directly onto surface of custard (this prevents a 'skin' from forming). Set aside to cool completely.
Spoon cold custard into baked pie shell and top with sliced fruit.
Serve the same day of making. Refrigerate any leftovers.
Before serving, sprinkle with a dusting of icing sugar.