You need to line 3 large baking sheets with parchment paper. The recipe makes large cookies and each pan can only fit 3-4 cookies. They spread a lot during baking
The baking time for each pan is about 14 minutes and that's why the total baking time is about 42 minutes. I highly recommend to bake one tray at a time for the best result
Prepare cookie dough:
Preheat the oven to 350 F (180 C) for conventional oven, 330 F (165 C) for convection oven. The rack is positioned in the middle of the oven
Combine all the dry ingredients and set aside. In a mixing bowl add softened butter (shouldn't be melty) and sugar. Cream using a paddle attachment on medium speed until light and fluffy, about 3-4 minutes. Scrape the side of the bowl.
Add the egg and vanilla and beat again for another 1-2 minutes. Scrape the bowl again. Sift in the dry ingredient mix. Switch to the lowest speed so the dry ingredients won't fly when you turn the machine on. Mix until just combined. It's okay if there is still some flour on the side of the bowl. Use a spatula to scrape the side of the bowl and fold everything in
Shaping:
Combine sugar with matcha powder. I didn't use the matcha powder for coating because my kids find it a bit bitter (though the adults won't mind it). They don't mind it when the matcha powder is mixed into the dough
Divide the dough into about 70 grams (about 2.5 oz) each. Roll into balls. Coat the dough ball in sugar mixture and then place on prepared baking sheets, about 3 inches apart. So I only managed to put about 4 cookies per half-sheet baking pan
Baking:
Put the baking sheet on the positioned rack. Bake for 8 minutes. Then wear the oven mitten and open the oven door, and carefully lift the baking sheet up and drop it down on the oven rack. Do this about 2 times. Quickly close the oven back down again. Bake for another 2 minutes. Repeat this action 2 more times every 2 minutes. So a total of 3 times. The total baking time is about 14 minutes. DO NOT overbake them
After the last round of 2 minutes of baking, remove the baking pan from the oven and bang the pan on the counter top one ore time and then let them cool down completely on the baking pan placed on top of a cooling rack. Don't try to move the cookies to the cooling rack for at least 10 minutes. They appear very soft at first, but will firm up with crisp edges and soft chewy center
Storage:
Once the cookies have cooled down completely, store them in an air-tight container for about 2-3 days. The baked cookies freeze well too. Simply keep them in freezer-friendly container and thaw at room temperature before serving