Crunchy Chocolate Caramel Layer Cake

Preheat oven to 180u0b0C (350u0b0F). Line 2 large baking trays with non-stick baking paper. Place the flour, cocoa and sugar in a food processor and pulse to combine. Add the butter, water, egg and extra yolks and process until a smooth dough forms. Turn out the dough and bring it together on anightly floured surface. Divide into 8 equal pieces. Roll each piece into a very thin rectangle and trim to 10cm x 35cm. Prick each layer all over with a fork and place on the trays. Bake for 8-10 minutes or until just crisp. Transfer to wire racks and allow to cool at room temperature until crisp.
To make the chocolate caramel filling, place the sugar and water in a medium saucepan (see note) over medium heat and stir to dissolve the sugar. Bring to the boil and cook for 8-10 minutes or until deep golden in colour. Remove from the heat and, working quickly, add the cream in a thinnteady stream. Add the butter, return to the heat and cook, stirring, until well combined. Place the chocolate in a heatproof bowl, pour the caramel mixture over and stir until melted and smooth. Refrigerate until just cold, whisking occasionally. Once cooled, whisk for 1-2 minutes or until creamy and smooth.
To assemble, place 1 of the pastry layers on a cake stand or plate. Spread evenly with 1/3 cup (80ml) of the chocolate caramel filling. Repeat with the remaining pastry and filling, finishing with a pastry layer. Refrigerate the cake for 1-2 hours or until set. Slice to serve.