Add sugar to softened butter and mix it into a smooth cream either manually with a whisk or using a mixer.
In a smaller bowl, beat the egg first, and then add half of it to the butter, mix, and then add the rest. Pay attention to the egg temperature; it should be similar to the butter or room temperature. If it's too cold, the butter may appear curdled.
Combine flour, matcha powder, baking powder, and a pinch of salt, and sift it into the butter mixture.
Work the dough and let it rest in the refrigerator for about 30 minutes. I recommend flattening the dough and wrapping it in plastic wrap.
It's easier to roll out the dough between two sheets of parchment paper. I let it chill in the refrigerator again after rolling it out to make it easier to handle during cutting and to prevent spreading while baking.
I cut the dough to approximately this thickness. You can go thinner, but you'll need to adjust the baking time accordingly.
Bake at 150 - 160 °C (300 - 320 F) for about 12 minutes. However, each oven varies, so it's better to monitor them to ensure they stay a nice green color and don't brown too much.