To make the pastry:

• In a large mixing bowl, mix together the flour and xanthan gum. Make sure your butter is really cold; if not, put it in the fridge or freezer until nicely chilled.
• Add the cubes to the bowl and, using your fingertips, rub the butter into the flour until it has a breadcrumb-like consistency. Make sure your hands are cool, as we want to avoid the butter getting warm! (You can also achieve the same result by using a food processor to blitz the ingredients together.)
• Stir in the sugar. Add the beaten egg and, using a knife, carefully cut it into the mixture until it comes together. It should form a ball and not be crumbly – it will be a little sticky to touch but not unmanageable.
• Wrap the dough in cling film (plastic wrap) and leave to chill in the fridge for around 30 minutes before using. You can freeze this pastry for up to 2 months; defrost fully before using.
• [Tip: Chill! Using cold butter and chilling the dough makes your gluten-free pastry stronger and more workable. Making any type of pastry on an incredibly hot day isn’t advisable, as the warmer your dough is, the more fragile it will become. However, make sure once chilled, you allow your pastry to warm up a bit before rolling, otherwise it will crack.]
  To make the pie:
   
• Remove the pastry from the fridge; if it feels really firm, leave it out at room temperature briefly before rolling it. remember not to handle the dough excessively as you work with it, as this will warm it up and make it more fragile. Lightly flour a rolling pin. on a large sheet of non-stick baking parchment, roll out the pastry to a 2mm (1⁄8in) thickness, into a large circular shape.
• Transfer the pastry to a 23cm (9in) fluted tart tin (pan). I do this by supporting the pastry as I gently invert it into the tin, with equal overhang on all sides. Peel off the baking parchment.
• Next, use your fingers to carefully ease the pastry into place, so that it neatly lines the tin. Lift the overhanging pastry and, using your thumb, squash 2mm (1⁄8in) of pastry back into the tin. This will result in slightly thicker sides, which will prevent the pastry case from shrinking when baked. Allow the overhang to do its thing – we’ll trim the overhang after chilling.
• Lightly prick the base of the pastry case with a fork, then place in the fridge for 15 minutes.
• Preheat the oven to 180°C fan / 200°C / 400°F.
• Once chilled, use a rolling pin to roll over the top of the tin, instantly removing the overhang and flattening down the pastry. next, loosely line the base of the pastry case with baking parchment and fill with baking beans (or uncooked rice if you don’t have any).
• Bake in the oven for 15 minutes, then remove the parchment and baking beans and bake for a further 5 minutes. remove from the oven, brush the base with beaten egg and pop back in the oven for a couple of minutes. The egg helps to seal the pastry when filled to prevent it from becoming soggy. Allow to cool completely and reduce the temperature to 160°C fan / 180°C / 350°F.
• For the filling, melt the butter, sugar and syrup in a small saucepan over a low heat. Allow to simmer for a minute or so, then remove from the heat and leave to cool for 10 minutes.
• Whisk the eggs briefly in a bowl with the cornflour, vanilla extract and salt. Gradually add the cooled butter and sugar mixture, whisking as you add it to ensure the eggs have no chance to cook (the mixture should be cool enough by now anyway!). Stir in the chopped pecans and pour the mixture into the prepared pastry case.
• Bake for 50 minutes or until puffed up and less wobbly. remove from the oven and allow to cool for a couple of hours until set. Slice and serve with custard, just how ouma used to like it!

Extracted from Gluten Free Xmas (Hardie Grant)