Preheat your oven to 170°C (150°C fan forced). Spray a square 20cm cake pan with oil, then line it with baking paper, leaving an overhang on the sides. Spray the paper with oil and line it with another sheet as well.

Using electric beaters, whip the butter and sugar together until pale and creamy.

Add the egg yolks and vanilla; beat until combined.

Sift the flour and baking powder over the buttery mix and mix until it starts to unite into a cohesive dough.

Turn the dough onto a lightly floured surface, dividing it into two equal portions. One half will serve as the base pressed evenly into the prepared pan.

Spread the raspberry jam over the base.

Roll out the remaining portion of the dough on a sheet of baking paper to form another 20cm square. If too soft, chill until manageable.

Invert this rolled-out pastry over the jam and remove the paper gently.

Bake for 25 minutes, or until golden brown.

Let it cool in the pan for 20 minutes, then transfer to a wire rack to cool completely.

Sift the icing sugar into a bowl and place the butter on one side.

Pour 1 tablespoon of boiling water over the butter, stirring until melted and smooth. Add more boiling water for a spreadable consistency.

Add a drop or two of pink food coloring.

Spread the icing over the cooled shortbread while it’s still wet.

Use a fork dipped in boiling water to rake enticing lines through the icing.

Allow it to set for an hour, then cut into squares to serve.