☆Preparation
Mix together flour and cornstarch.
Line a baking sheet with parchment paper or a silicone mat.

Cream the butter until smooth, then gradually add in the granulated sugar in three portions, mixing well each time.
Use an electric hand mixer to beat on low speed for 2-3 minutes until whitish. During the process, scrape down the batter twice.

Switch to a spatula and add vanilla oil, mix well. Add ground almonds and mix until smooth while crushing lumps.
Sift the cake flour and cornstarch over the mixture.

Fold it as if you were cutting it. Fold it until a lot of yellowish small lumps form.

Press it into a bowl to flatten it. Gather it in the center and repeat twice more (for a total of three times).

Take 20g each and shape into 15 balls. Flatten them lightly. Coat each ball with sugar.
Chill in the freezer for 20-30 minutes before baking. Bake at 170℃ / 338 F for 24 minutes (preheat the oven to 190℃ / 374 F).

Once cooled on the baking sheet for 5 mins, transfer to a rack and cool completely. It tastes good crispy and crumbly.
Store them in an airtight container at room temperature. Best eaten within 4 days.