Roll pastry to fit square baking tray cutting off excess pastry. Place one square of pastry on large ungreased oven tray. Bake in very hot oven 5 to 10 minutes or until well browned. Repeat process for pastry squares. Flatten puffy side of baked pastry with hand.

Line square baking tin with foil bringing foil up the sides: this makes it easy to remove slice when set. Place one piece of pastry into base of tray, flattened side uppermost. Combine sugar, cornflour and custard powder in heavy based saucepan, mix well to combine. Blend with a little milk until smooth, stir in remaining milk; add butter. Stir mixture constantly over heat until custard boils and thickens, reduce heat, simmer 3 minutes. Remove from heat, quickly stir in vanilla, then stir in beaten egg yolks. Pour 2/3 of hot custard over