Preheat oven to 170 C (340 F) and grease a 9 inch round pie dish then line with baking paper.

In a large bowl, sift sugar, flour, cocoa powder and salt together then whisk to combine well.

With your finger tips, rub the butter into the flour mixture, add vanilla extract. Try not to over work the dough.

Press the dough into the prepared dish. For a smooth look, roll a glass jar over the dough and if desired, use a fork to make a pretty pattern around the edge. Bake for 30 -40 minutes (bake longer if you would like your shortbread crispy, and less if you like it soft and fudgy).

Whilst still warm, gently slice the shortbread into wedges. Remove wedges from dish once completely cool and dip them in the melted chocolate and cover with sprinkles. Place wedges on baking paper whilst the chocolate sets.