Marbled Dark and White Chocolate Squares

Method

1 Grease and line the base of a 20cm (8in) square, loose-bottomed cake tin with baking parchment. Place the biscuits in a food processor and blend until they form fine crumbs, then stir in the melted butter. Press down into the tin to make an even layer. Chill for 1 hour.

2 For the filling, place the butter and sugar in a non-stick pan over a low heat, stirring until the butter melts and the sugar dissolves. Add the condensed milk and bring gently to the boil, stirring continuously, to make a golden caramel. Remove from the heat. Carefully spoon the caramel evenly over the biscuit base. Return to the fridgeto chill for 1-2 hours or until set.   

3 Melt the dark and white chocolate in separate bowls over pans of gently simmering water and stir half of the oil into each. Pour the dark chocolate over the caramel, spreading it out to the edges. Repeat with the white chocolate, but swirl with a fork to create a marbled pattern. Set aside. When the chocolate has hardened a little, cut into squares and serve.