1.Make pastry. Process sifted flour and sugar with butter until crumbly. Add enough of the water until ingredients just come together when processed. Knead dough on floured surface until smooth. Cover; refrigerate 30 minutes.
2.Grease 12.5cm x 35cm (5-inch x 14-inch) loose-based fluted flan tin. Reserve one-quarter of the dough for decoration. Roll remaining dough between sheets of baking paper until large enough to line tin. Ease dough into tin; press into base and sides. Trim edges; prick base all over with fork. Refrigerate 30 minutes.
3.Roll out reserved dough on floured surface, cut out 12 x 2cm (3/4-inch) rounds from reserved dough; place on baking-paper- lined tray. Refrigerate 30 minutes.
4.Preheat oven to 200°C/400°F.
5.Blend or process nuts finely.
6.Beat butter and sugar in small bowl with electric mixer until light and fluffy. Beat in eggs, one at a time. Transfer mixture to medium bowl; stir in sifted flour and cocoa, and nuts. Spread jam over base of pastry case; top with pistachio filling. Top filling with pastry rounds. Bake 15 minutes.
7.Reduce oven to 180°C/350°F; bake further 25 minutes. Cool.
8.Dip extra nuts in chocolate; place on pastry rounds. Cool before slicing.
If you don’t have a rectangular flan tin, you could use a 22cm (83/4-inch) round loose-based fluted flan tin for this recipe.Note