Break up the dark chocolate.

Break up the white chocolate.

Fit the K beater to the machine.

Pre heat the oven to 180ºC.

Line the square tin with parchment paper.

Add Ingredients 1 (flour, sugar, butter) into the Mixer bowl.

Attach the Mixer bowl to the machine and fit the splash guard.

Mix on speed 5 for 2 minutes.

Press the shortbread mixture into the base of the tin and level.

Bake for 20 minutes at 180ºC.

Leave to cool.

Add the first 2 items of Ingredients 2 (butter, sugar) to the large saucepan.

Heat over a medium heat, stirring often until the mixture has come together.

Add the rest of Ingredients 2 (condensed milk) to the saucepan.

Bring to the boil, stirring constantly. Ensure you scrape along the bottom of the pan while stirring so no mixture sticks and burns.

Lower the heat.

Simmer for 2 minutes, while stirring.

Remove from the heat and let cool, stirring occasionally.

Once the caramel is cool, poor onto the shortbread and level.

Place the square tin in the fridge.

Leave to cool.

Add Ingredients 3 (dark chocolate) into a small glass bowl.

Heat until melted.

Let cool slightly.

Pour onto the caramel and level.

Add Ingredients 4 (white chocolate) into a small glass bowl.

Heat until melted.

Transfer the white chocolate into the piping bag.

Pipe the white chocolate over the dark chocolate.

Let cool.

Cut into squares.

Serve.