1.Place rhubarb and sugar in medium saucepan; cook over low heat, stirring, until sugar dissolves and rhubarb softens.
2.Preheat oven to moderately hot. Grease oven tray.
3.For the filling, beat butter, vanilla and sugar in small bowl with electric mixer until thick and creamy. Add egg; beat until combined. Stir in flour and almond meal.
4.Cut one pastry sheet into 14cm x 24cm rectangle; cut remaining pastry sheet into 16cm x 24cm rectangle. Leaving 2cm border around all sides, make about eight evenly spaced slits across width of larger pastry piece.
5.Place smaller pastry sheet on greased oven tray; spread with jam. Place filling on pastry, leaving 2cm border around the edges; top filling evenly with rhubarb mixture. Brush around border with egg white. Place remaining pastry sheet over filling; press edges of pastry together to seal.
6.Brush jalousie with remaining egg white; sprinkle with extra sugar. Bake, uncovered, in moderately hot oven about 35 minutes or until jalousie is browned lightly and cooked through. Serve warm or cool with vanilla ice-cream, if desired.
You need approximately four large trimmed stalks of rhubarb for this recipe.Note