Whisk together the almond flour, oat flour, corn starch, matcha, and salt in a medium bowl. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment or a medium bowl with a hand mixer, beat the butter on high until light and fluffy.
Slowly add the powdered sugar and beat until incorporated.
Add the vanilla and mix until smooth.
With the mixer on low, slowly add the dry ingredients to the butter and beat until completely smooth, scraping down the sides as necessary.
Roll the dough into a ball and flatten into a disc. Wrap in plastic and chill for 1-3 hours.
When ready, roll the chilled dough out into a ¼-inch thick oval onto a piece of parchment paper dusted with oat flour. Use a cookie cutter to cut out trees (or your other favorite shape). Using a knife or bench scraper as needed to lift the cookies, transfer cookies to a parchment lined baking sheet, 1-2 inches apart. Repeat until you've filled your baking sheets.
If desired, sprinkle sanding or coarse sugar over the cookies.
Freeze the baking sheet with the cut-out cookies for at least 10 minutes while you preheat the oven to 350°F.
Bake cookies, one tray at a time, on the middle rack for 11-12 minutes, until the bottom edges just begin to turn golden. Let cool completely on the baking sheet. Repeat.
Meanwhile, fill a small saucepan with a few inches of water and set a heat-proof bowl over the top. Being careful not to get any water in your bowl, add about 3 ounces of the chopped white chocolate. Cook, undisturbed until a little more than half is melted, then stir until the rest melts. Cook for a few minutes longer until the chocolate stings a little when touched on your wrist or just below your lower lip. Remove the bowl from the heat (again being careful not to get any water in it) and add the reserved 1 ounce of chocolate. Stir until the chocolate melts. Let sit, stirring occasionally, for 2-3 minutes. Transfer the melted chocolate to a small piping bag fitted with a small round tip.
When the cookies are cool, drizzle the white chocolate over the trees like a garland of lights.
Add pearl sprinkles lights, if desired, or dot the lights on with white chocolate.
This nutritional information has been automatically calculated, and as such, may be incomplete or inaccurate. Please reference the specific ingredients you use for the most accurate nutritional information.