Galette des Rois with pistachio cream

In a bowl, mix the softened butter with the icing sugar until creamy.
Add the eggs one by one, mixing well after each addition.
Add the almond powder, pistachio powder and, if desired, the pistachio paste for a more intense flavor. Mix until smooth.
Assemble the galette:
Roll out a sheet of puff pastry on a baking sheet covered with baking paper.
Spread the pistachio cream in the center, leaving about 2 cm of free edge.
Insert the bean into the cream.
Cover with the second sheet of puff pastry and press the edges to seal them.
Decorate and brown:
With the tip of a knife, draw patterns on the top of the galette without piercing the dough.
Mix the egg yolk with a tablespoon of water or milk, then brush the galette with this mixture to brown it.
Leave to rest for 30 minutes in a cool place to prevent the dough from losing its shape during cooking.