Stir the room temperature butter until creamed, add sugar and whisk together.

Add egg yolk and mix in.

Add vanilla essence and continue mixing.

Combine matcha and flour, sift into the bowl, and use a spatula to mix in.

It's done once it's well incorporated like the photo. Wrap in plastic wrap, roll into a tube, and let it sit in the freezer for 20 minutes.

Slice into 5 mm and top with chopped walnuts, as you like. Bake in an oven preheated to 355°F/180°C for 15 minutes.