Add the TREX and sugar to a large bowl and cream together using an electric hand mixer till the mixture is light and fluffy.
Mix in the orange juice and vanilla extract. Then add in the flours, chopped pistachios and salt and mix until you get a soft dough. If the dough is a little bit sticky then add in a tbsp or two of flour. If dough is to dry, add a tsp or two of water.
Split the dough into two and shape each one into a disc, wrap in plastic wrap and chill for 1 hr minimum.
Preheat oven to fan assisted 150C / 170C / 325F / gas 3.
Take the first disc of dough from the fridge, roll it out on a lightly floured surface till it is about 5mm thick and then cut into your desired shapes (I use a 6cm diameter cutter) and lay on a lined baking sheet.
Quickly scoop up the excess of dough, reshape, roll out and cut again. Repeat with the second disc of dough. You can freeze some of the cut shortbread at this stage.
Bake the shortbread for 12-14 mins until they are lightly golden.
Let the shortbread cool on the tray for about 10 mins before transferring it to a cooling rack to cool completely.
Serve with extra pecans dotted around.