Cream together the softened butter and powdered sugar until light and fluffy, about 3-4 minutes.
Add the egg yolks and sour cream, mixing until well combined.
In a separate bowl, whisk together the flour, fine ground pistachios, baking powder, and baking soda. Gradually add to the wet ingredients and mix until just combined.
Wrap the dough in plastic wrap and refrigerate for at least 1 hour.
Preheat your oven to 180°C (350°F) and line baking sheets with parchment paper.
Roll the chilled dough out and cut into shapes, placing on prepared baking sheets.
Bake for 10-12 minutes or until edges are lightly golden. Cool on wire racks.
Combine pistachio cream, softened butter, and orange blossom water in a bowl and mix until smooth.
Spread the filling on the flat side of one cookie and top with another to create a sandwich.
Heat heavy cream and butter, remove from heat, add chocolate chips, and stir until smooth to make ganache.
Drizzle ganache over filled cookies and allow to set before serving.
