With a handheld mixer in a large bowl, cream the butter with the sugars until fluffy, 2 to 3 minutes. Add the egg and vanilla, beating for about 1 minute. Sift the salt with the flour and matcha. Reduce the mixer to a low speed and then add the flour mixture, mixing just until blended.
Turn the dough out of the bowl. Shape into a disc, cover with plastic wrap and chill for 1 hour.
Remove from the fridge and dust your cookie cutters, rolling pin and workspace with flour. Use a rolling pin to roll out the dough about 1/4-inch thick and cut out with assorted cutters. Place on 2 parchment-lined baking sheets.
Bake until the edges of the cookies are a light golden, about 15 minutes. Transfer the cookies to a rack to cool. Decorate with royal icing, sanding sugar and sprinkles if desired.