Add the butter 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 Baileys. Then add in the flours, chopped pistachios, salt and mixed spice 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.
Split the dough into two and shape each one into a disc, wrap in plastic wrap and chill for 1hr 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 re shape 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 about 12 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.
Make the glaze by melting the chocolate and mixing in the bailey.
Dip half of each shortbread cookie into the chocolate Baileys mix, let the excess chocolate drip off, sprinkle on some pistachio dust and let the chocolate harden.
Then dig right in.