1: Pour 100 g flour, 150 g oat flour, 125 g brown sugar, 125 g butter, 1 egg, 5 g salt, 20 g powdered cocoa into the bowl of a mixer.
2: Knead for 1 or 2 minutes until smooth.
3: Place the ball of dough on a sheet of cling film, flatten it into a square cake about 1 cm thick, then close the cling film and put it in the fridge for 1 hour.
4: Remove the dough from the cling film and roll out to 1/2 cm thickness. Preheat oven to 180°C (360°F).
5: Cut out the shapes of your choice, in this case small rectangles, and place them on a sheet of baking paper on a baking sheet.
6: You can add chocolate chips to the top of each shortbread.
7: Bake for 15 minutes.
8: Cool on a wire rack and store in a sealed tin or jar.
Remarks
Don't cook for too long, as the shortbread should remain soft.