2) Alternatively, make the dough in a food processor. With the machine fitted with the metal blade, pulse the flour, sugar, and salt until combined. Add the butter and pulse until it resembles yellow cornmeal mixed with bean-sized bits of butter, about 10 times. Add the egg and pulse 1 to 2 times; don't let the dough form into a ball in the machine. (If the dough is very dry add up to a tablespoon more of cold water.) Remove the bowl from the machine, remove the blade, and bring the dough together by hand.
3) Form the dough into a disk, wrap with cling film, and refrigerate until thoroughly chilled, at least 1 hour. On a lightly floured surface, roll the dough with a rolling pin into a 30cm circle about 0.25cm thick. Transfer the dough to a 23cm pie dish and trim the edges, leaving about an extra 2.5cms hanging over the edge. Tuck the overhanging dough underneath itself to form a thick edge that is even with the rim. Flute the edge as desired. Freeze the pie shell for 30 minutes.
4) Set separate racks in the centre and lower third of oven and preheat the oven to 200C/Gas 6. Put a piece of baking paper or foil over the pastry case and fill with dried beans or pie weights. Bake in a baking tray on the center rack until the dough is set, about 20 minutes.
5) Remove the pastry case from the oven and lift sides of the baking paper to remove the beans. Continue baking until the pastry case is lightly golden brown, about 10 more minutes. Reduce the oven temperature to 180C/Gas 4.
For the filling:
1) In a medium saucepan, combine the butter, brown sugar, golden syrup and salt. Bring to a boil over medium heat, and stirring constantly, continue to boil for 1 minute.
2) Remove from the heat and stir in the nuts, bourbon and the vanilla. Set the mixture aside to cool slightly, about 5 minutes. If the pastry case has cooled meanwhile, return it to the oven for 5 minutes to warm through.
3) Whisk the beaten eggs into the filling until smooth. Put the pastry case on a baking tray and pour the filling into the hot crust.
4) Bake on the lower oven rack until the edges are set but the centre is still slightly loose, about 40 to 45 minutes. (If the edges get very dark, cover them with aluminium foil half way during baking.) Cool on a rack. Serve slightly warm or room temperature.