Preheat the oven to 180°C/ 160°C fan/ gas mark 4/ 350°F
Line the tin with baking parchment or magic liner or lightly grease with butter
Sieve the cocoa powder.
For the Chocolate Shortbread:
Beat the butter, sugar, and vanilla extract together with a hand mixer or stand mixer
Add the flour, semolina, sieved cocoa, baking soda, and salt and mix slowly until all the ingredients are combinedDon’t overwork the dough or it will go oily
Put the dough into the baking tin and spread out, using your fingers to push it into the corners. Flatten with the back of a spoon then use the edge of the spoon to pull down any excess from the sides of the tin
Cook the shortbread for 30 minutes or until firm to the touch
While it's still hot, cut the shortbread carefully into 16 fingers or 32 squares
Cool for about 20 minutes in the pan and remove to a wire cooling rack until completely cool
Dust with icing sugar before serving.
Notes
EverydayCooks tips:
You could cut the biscuits into 16 fingers if you want a larger piece
If you don't have any semolina, add the extra weight in flour