Preheat your oven to 180°C and line your square baking tin with non-stick baking paper very carefully today. Leave a little paper hanging over the edges so you can lift the finished shortbread out easily later.

Rub the flour and cold butter together in a bowl until the mixture looks like fine, golden breadcrumbs. Stir in the caster sugar and knead the dough gently until it comes together in a smooth ball.

Press the shortbread dough into the bottom of the tin and prick it all over with a fork. Bake for twenty minutes until it is light golden brown, then let it cool completely in the tin.

Combine the butter, muscovado sugar, and condensed milk in a heavy-based saucepan over a very low heat today. Stir constantly until the butter has melted and the sugar has completely dissolved into the creamy milk.

Increase the heat slightly and bring the caramel mixture to a gentle, bubbling boil for about ten minutes. You must stir continuously to prevent the sugar from burning on the bottom of your hot saucepan.

Pour the thick, golden caramel over the cooled shortbread base and spread it out evenly with a spatula. Let the caramel set at room temperature for at least one hour until it feels firm and cold.

Place the milk and dark chocolate in a heatproof bowl over a pan of gently simmering water today. Stir slowly until the chocolate is completely melted, glossy, and very smooth without any small lumps remaining.

Pour the melted chocolate over the set caramel layer and spread it to the corners with a knife. You can use a fork to create a pretty wavy pattern in the chocolate before it starts setting.

Leave the Millionaire Shortbread to set in a cool place or the refrigerator for at least two hours. This ensures the layers bond together and the chocolate becomes firm enough to cut into neat, clean squares.

Lift the shortbread out of the tin using the paper and cut it into sixteen even, delicious squares. Use a hot knife to slice through the chocolate and caramel smoothly for a very professional finish today.