In the bowl of a food processor, ground the macadamia nut into meal as fine as possible without turning it into nut butter. Transfer to a small bowl, add flour and salt, and mix thoroughly, breaking up any lumps.
Warm the stand mixer mixing bowl under running hot water for ten seconds. Beat softened butter in the warm mixing bowl with the paddle attachment until the consistency is of mayonnaise. Add powder sugar and combine on low speed, then increase speed and beat until fluffy.
Add half the macadamia nut meal mixture to the butter, mix on low speed until completely combined. Add the rest and mix on low speed again until completely combined. Scrape the side and bottom of the bowl as necessary.
In a small bowl, add egg and vanilla extract, whisk to combine. Pour egg mixture into the mixing bowl and beat on low until completely combined and smooth. Refrigerate mixture for at least 2 hours.
Preheat oven to 350°F.
Add the unsweetened shredded coconut to a plate in an even layer.
Slice the croissants in half, spread about 3 tablespoons of macadamia cream on the bottom halves, replace the top halves and spread about 1 tablespoon of macadamia cream on top.
Flip the croissants over and dip the outer surface with the macadamia cream into the plate of shredded coconut. Press it lightly to flatten and to allow coconut flakes to adhere to the cream. Flip the croissant on its back and on to a parchment line baking sheet.
Bake for 20 minutes. Remove from the oven and allow to cool on a wire rack.
Serve with a generous dusting of powder sugar.