Heat the oven at 180C and prepare an oven tray
Combine softened butter, icing sugar, and vanilla. Whip up this for 5 minutes.
Introduce the egg into the mix and stir. Now, incorporate the ground pistachios, corn flour, salt, and milk. Aim for a thick yet spreadable mixture. If it appears too thick, just sprinkle in a tad more milk until you reach the perfect consistency.
Cut the croissants horizontally using a bread knife.
Pipe the pistachio buttercream in the croissants then place the other half on top. Add a little more buttercream on top of the croissant, then sprinkle with the remaining pistachios.
Bake for 15 minutes until the mixture has melted and until the top of the croissant is golden. Dust with Icing sugar and enjoy warm!
