Combine all of the inner ‘fat’ pastry ingredients together into a dough and refrigerate for 30 minutes. Do the same for the outer egg pastry and refrigerate for 30 minutes as well.
Shaping and Folding
On a floured surface, roll out the first dough into a 20 cm (8 inch) square, then roll out the egg dough into a 30 cm (12 inch) square. Place the smaller pastry square in the middle of the egg pastry square, so that the edges of the inside square are at a 45° angle to the edges of the outer square. Fold in the corners of the outer square over the inner square. Pinch the seams of the outer dough closed. Rest in the refrigerator for 30 minutes, then roll out the combined dough into a long rectangle, 5 mm (¼ inch) thick, making sure that the top and bottom edges of the rectangle are parallel to the rolling pin. Fold in each end like an envelope and return the dough to the refrigerator for another 30 minutes. Repeat the process two to four times, resting the pastry each time for 30 minutes. Grease and flour 30 small tart (flan) tins approximately 6 cm (2½ inches) along the base and 9 cm (3½ inches) in diameter (disposable mince pie foil cases or similar are ideal). To finish, roll out the pastry to a thickness of 5 mm (¼ inch) and use a cutter to cut out circles that are large enough to line the tins. Place the circles of pastry into the tins and refrigerate.
Preheat the oven to 180°C (350°F/Gas 4). In a saucepan, dissolve the sugar in the water over low heat and let it cool for 5 minutes. Blend the cornflour with 1 tablespoon of the evaporated milk, then mix in the rest of the evaporated milk, the eggs and the yolks. Whisk this mixture into the sugar water until combined.
Place the tins lined with pastry on a baking tray, fill them with the custard and bake, lowering the oven temperature to 150°C (300°F/Gas 2). Cook for 35 minutes until the filling is set but still a little wobbly.