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.
Wrap the dough up in clingfilm and chill it in the fridge for at least 30 minutes. This step stops the biscuits spreading when baking.
Preheat oven to 170°C / 150°C Fan / 325°F / Gas Mark 3. Line two large baking trays with parchment paper.
Lightly flour a work surface with extra flour, roll the shortbread dough out until it's roughly the thickness of a pound coin. Take a 6cm heart cutter, and cut out roughly 20 from the dough, re-rolling and continuing to cut out more biscuits.
Transfer the unbaked shortbread biscuits onto the baking trays, sprinkle with a little extra sugar, and bake for 15-20 minutes until pale golden in colour - you don't want these too golden. They should be slightly firm to the touch when ready. Allow to cool for 5 minutes on the baking trays, then move to a wire rack and leave the biscuits to cool completely on there.
Once the biscuits are cool, melt the two types of chocolate. Dip one biscuit at a time on one side into the chocolate. Allow to set, before drizzling the remaining chocolate on each biscuit. Finish with some sprinkles of your choice.
Once the chocolate has set, the biscuits are ready to enjoy. They'll keep in an airtight container/tin for up to 1 week.