Pre heat the oven to 170°C.
Line a baking sheet with parchment paper and stand an 18cm fluted flan ring on top.
Sift the flours into a bowl, add the sugar and butter and rub in the butter using your fingertips.
Add the chocolate and work the mixture together using your hands until it starts to form a soft crumbly dough.
Spoon into the tin and pack down with the back of a metal spoon before pricking all over with a fork.
Cook for 35 minutes until pale golden brown. Sprinkle with 2tsp of caster sugar and score into 8 pieces whilst hot. Leave to cool for 5 minutes.
Serve warm with a cup of tea or coffee.
If you don't have a flan ring the shortbread can be made in a sandwich tin instead. This shortbread will keep for up to 3 days in a poly box.
Please note: this recipe has been created and uploaded by a member of the Tesco Real Food online community. Tesco does not test customer recipes so cannot accept responsibility for the content, validate the results or answer queries regarding them.