1. Make up the half quantity of shortbread as directed here, pressing it thinly in the tin. Bake for about 50 minutes and leave in the tin, uncut, to cool.
2. For the toffee filling, put the butter, sugar, syrup and condensed milk in a saucepan and heat gently, stirring until the sugar dissolves. Raise the heat and bring the mixture to a gentle boil, stirring all the time, and simmer gently for about 5 minutes until the mixture has thickened and is a creamy fudge colour. Pour over the shortbread and allow to cool.
3. Break the chocolate into three small heatproof bowls and place the bowls over saucepans of gently simmering water. Allow to melt, then remove from the water.
4. Place alternate teaspoonfuls of the melted chocolate on top of the toffee. Tap the tin on the work surface so that the chocolates merge together, then drag a skewer through the chocolate to create a feathered effect. Tap the tin again to smooth the chocolate and set aside in a cool place until firm. If the chocolate sets too firm (in the fridge) it will be more difficult to cut.
5. Use a sharp knife to cut the shortbread into 24 equal pieces (it is very rich so don't be tempted to cut fewer, larger pieces!), and carefully lift from the tin. Chill until required, but stand at room temperature for a few minutes before serving.
1/2 quantity 
Quick & Easy: 30 minutes or less
Healthy Recipe: low fat and/or calories
Kid-Friendly: extra nutrition and/or fun!
Low-Carb: low carbohydrates
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