Preheat oven to 180°C / 160°C Fan / 350°F / Gas Mark 4. Line a 20cm / 8-inch square cake tin with parchment paper and set aside.
Start by preparing the shortbread dough - cream the softened butter and sugar until light and creamy.
Now add the flour and the semolina, mix until a crumbly dough forms. Be careful not to overwork the dough at this point, only mix until it comes together. Now fold through the chopped chocolate.
Transfer shortbread dough to a 20cm / 8-inch square cake tin and press down gently. Carefully score 12 squares from the dough, making sure not to cut all the way through. Bake for 25-30 minutes until slightly golden in colour. Leave the shortbread to cool for 5 minutes, then using a sharp knife, slice all the way through where you scored the shortbread before baking.
Finally, sprinkle with a small amount of extra sugar before devouring! The shortbread will keep in an airtight container at room temperature for up to one week.