Sift powdered sugar; set aside. Sift cake flour twice; set aside. Cream unsalted butter until soft.

Add the powdered sugar in 3 parts. Mix each time until combined. Mix it with a hand mixer on low speed until it becomes white and fluffy.

Scrape the batter on the inner side of the bowl and mix it.

Add egg yolk. Mix it with a hand mixer on low speed until combined. Scrape the batter on the inner side of the bowl and mix it.

Take the batter adhering to the hand mixer and place it in the bowl. Add vanilla oil and mix it until combined.

Add almond flour. Mix it until combined while crushing lumps.

Add all the flour. Mix it while cutting it, scooping sometimes. Mix it until the large lumps form. It's okay the dough seems to be powdery at this stage.

Take the dough out from the bowl. Press lightly to flatten, cut in half and stack one on top of the other.

Repeat it until powderiness disappears or smooth. (about 12times) When it becomes smooth, the dough won't stick to your hand.

Shape it square and cut in half. Wrap each with plastic wrap. You can bake cookies for one baking tray with half of the dough. Let it sit in a fridge overnight.

Next day, take the dough out of the fridge, leave it for 15-20 mins. Press it to soften. Roll it out into 5mm (0.2'') thick while coating it lightly with bread flour.

Cut it with cookie cutters and press cookie stamp onto it. Take off each cookie gently not to lose it's shape and put them on a tray. It's easy to take off if you touch it through plastic wrap.

Re-roll the dough scraps and cut again. Place the cookies in the freezer for 1 hour to keep the trace of the stamp.

Preheat an oven to 190℃ / 374 F. Take the cookies out from the freezer and put them on a baking tray. Bake it at 170℃ / 338 F for 15-17 mins. (cookie size 4.5 cm / 1.8 inch→Bake for 15mins, cookie size 6 cm / 2.4 inch→Bake for 16-17mins)

Cool them down well. Freshly baked cookies are soft but become crisp when cooled. If you put them in a closed container, they will keep crispy texture for about 3 days.