Chop the Oreo cookies into small pieces.

Mix cake flour, baking powder, and Oreo crumble in a bowl.

Combine room-temperature egg, vegetable oil, and sugar until emulsified.

Add the sifted dry ingredients to the wet mixture.

Mix until the dough comes together, then add the chopped Oreo pieces.

Shape the dough into a 2cm thick rectangle on a baking tray.

Bake in a preheated oven at 180°C for 25 minutes, then let cool slightly.

Cut the biscotti into desired sizes while still warm.