In a large bowl, cream together the butter, powdered sugar, and vanilla extract until smooth.
Add the egg yolks and sour cream, mixing until fully combined.
In a separate bowl, combine the flour, ground pistachios, baking powder, and baking soda. Gradually add this dry mixture to the wet ingredients, mixing until a dough forms.
Wrap the dough in cling film and refrigerate for at least 2 hours.
When ready to bake, roll the chilled dough between two sheets of parchment paper to approximately ½ cm (0.2 inch) thickness.
Using a round cookie cutter, cut out shapes and place them on a baking tray lined with parchment paper or a silicone mat.
Bake at 180° C (356° F) for 15 minutes, rotating the tray halfway through baking. Allow cookies to cool completely before assembly.