The beauty of millionaire's shortbread is that it can be adapted to suit your taste. Like thicker shortbread and caramel layers? Make it in a 20cm/8in square tin and bake the shortbread for ten ...

The beauty of millionaire's shortbread is that it can be adapted to suit your taste. Like thicker shortbread and caramel layers? Make it in a 20cm/8in square tin and bake the shortbread for ten ...

Line two 8-inch square baking tins with parchment ... Pour the caramel over the shortbread using a spatula to get it all out of the saucepan. Spread it out and set it aside to cool.

Pop the cake tin in the oven and bake for 20 to 25 ... use a sharp knife to cut it into pieces and your delicious homemade millionaire shortbread is now ready to serve.

So what gives this slice its multi-millionaire status? "It's mainly about the shortbread," says Jo. "I actually use a gluten-free flour blend as it stays crisp and light compared to a wheat flour ...