2) 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) Alternatively to make the dough by hand, in a medium bowl, whisk together the flour, sugar and salt. Using your fingers, work the butter into the dry ingredients until it resembles yellow corn meal mixed with bean-sized bits of butter. (If the flour/butter mixture gets warm, refrigerate it for 10 minutes before proceeding.) Add the egg and stir the dough together with a fork or by hand in the bowl. If the dough is dry, sprinkle up to a tablespoon more of cold water over the mixture.
4) Form the finished dough into a disk, wrap with cling film and refrigerate until thoroughly chilled, at least 1 hour.
5) On a lightly floured surface, roll the dough into a 30cm circle about 0.25cm thick with a rolling pin. Transfer the dough to a 23-cm pie pan and trim the edges, leaving about an extra 2.5cm 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 pastry case for 30 minutes.
6) Set separate racks in the centre and lower third of oven and preheat to 200C/Gas 6. Put a piece of parchment paper or foil over the pastry case and fill with dried beans or pie weights. Bake on a baking sheet on the centre rack until the dough is set, about 20 minutes.
7) Remove from the oven and lift sides of the parchment paper to remove the beans. Continue baking until the pie shell is lightly golden brown, about 10 more minutes. Cool on a rack. Lower the oven temperature to 180C/Gas 4.
To make the pie:
1) While the pie shell is cooling make the filling. In a large bowl, whisk together the pumpkin, brown sugar, eggs, half-and-half, spices and salt until smooth. Return the pastry case to the baking sheet and pour in the filling.
2) Bake on the lower oven rack until the edges of the filling are set but the centre is still slightly loose, about 50 to 60 minutes. (If the edges get very dark, cover them with aluminium foil.) Cool on a rack. Serve room temperature or slightly warm.