Preheat your oven to 350 degrees. Line three baking sheets with parchment and set aside.
In the bowl of a stand-up mixer with the paddle attachment, add the butter and sifted powdered sugar. Beat until light and fluffy, about 2 minutes. Add the egg and vanilla extract. Beat once more until combined, scraping down the sides as needed.
Pour in the flour, baking powder, salt and water and mix one last time until smooth. Transfer the batter to a piping bag fitted with a small-ish round tip. (Mine was in between a number 8 and a number 10.)
Pipe 5 to 6 inch lines of the batter onto the baking sheet. (I just eyeballed this measurement but if you like you can draw lines with a pencil and then flip the parchment over and trace the lines with the batter.) Repeat until you’ve done about 30 lines per baking sheet. Bake the pocky, one baking sheet at a time, for 10 to 12 minutes, until lightly golden brown around the edges. Leave on the baking sheets to cool completely.
Meanwhile, divide the white chocolate amongst two bowls. Melt the white chocolate in the microwave for 1 minute, stirring at the 30 second mark. Sift the matcha into one of the bowls with the white chocolate and stir until combined.
Ok, so the pocky is not the sturdiest. It’s somewhat fragile. So to decorate them, I simply spooned a bit of white chocolate over about half of the pocky (see photo) and then scraped the sides, gently, with a small offset spatula or butter knife, to remove any excess chocolate. I transferred it to a baking sheet and then sprinkled on any of the toppings above. Repeat until you’ve worked your way through all of the pocky.