In a large bowl, cream the softened unsalted butter and granulated sugar. Add the vanilla, egg, and beat until smooth. Set aside.
In a separate bowl, whisk together the all purpose flour, almond flour, matcha powder, and salt. Add the flour mixture to the butter mixture and stir until combined. Cover the bowl and let it rest in the fridge for a couple hours.
Put the cookie dough between two sheets of parchment paper and using a rolling pin, roll the cookie dough until it's ⅛in/⅓cm. Stick the rolled out cookie dough into the freezer for 5 minutes to let it solidify.
Preheat the oven at 325°F/160°C while the dough is chilling.
Cut the cookies out using a tree shaped cookie cutter. If the dough starts to soften, stick it back in the freezer for another 5 minutes before taking the cut out cookies onto a baking sheet. You can gather the scraps of dough and re-roll as much as needed.
Bake the cookies for about 18 to 20 minutes. Let them cool for about 10 minutes before transferring them to a wire rack to cool completely.
Melt the white chocolate in a double boiler and dip the tops of the cookies and set them on a wire rack. Sprinkle with white nonpareils and let the chocolate cool to solidify.