Cut the butter into cubes and add to the dry ingredients. Mix the dough and then add the egg. Put the dough in the fridge. When the dough is cold, roll it out to a thickness of 3 mm. and use a dough-cutter to make the pastry biscuits. Put the biscuits onto a baking tray.
Bake the biscuits in the oven at 180 degrees Celsius for approx. 8-9 minutes until the edges turn golden. Take them out and let them cool.
Scrape the seeds from the vanilla pod. Put all the ingredients (including the hollowed out vanilla pod) into a heavy-bottomed saucepan. Whisk thoroughly.
Keep stirring at medium heat and let the cream boil for one minute. Allow the cream to cool completely and put it into a piping bag.
Whip the cream and fold in the blackberry jam. Put the cream mixture into a piping bag with a large star-shaped nozzle.
Mix all the ingredients together. Stir until the icing is uniform.
Apply the icing onto half of the pastry biscuits. Pipe two circles of blackberry cream onto the rest of the biscuits.
Fill the void with cream.
Chop the pistachios.
Place the iced biscuits on top and decorate with blackberry cream and a fresh blackberry. Finally, sprinkle the chopped pistachios on top.