Millionaires' Shortbread

1. Pre-heat the oven to 180(C)/Gas mark 4, or 356(F). Lightly grease a 13 x 9inch (33x23cm) Swiss roll tin. 250g plain flour 75g caster sugar 175g butter, softened 2. To make the shortbread, mix the flour and caster sugar in a bowl. Rub in the butter until the mixture resembles fine breadcrumbs. Knead the mixture together until it forms a dough, then press into the base of the prepared tin. Prick the shortbread lightly with a fork and bake in the pre-heated oven for about 20 minutes or until firm to the touch and very lightly browned. Cool in the tin. For the caramel: 100g butter or margarine 100g light muscavado sugar 2 x 397g cans condensed milk 3. To make the caramel, measure the butter, sugar and condensed milk into a pan and heat gently until the sugar has dissolved. Bring to the boil, stirring all the time, then reduce the heat and simmer very gently, stirring continuously, for about 5 minutes or until the mixture has thickened slightly. Pour over the shortbread and leave to cool. 200g plain or milk chocolate, broken into pieces 4. For the topping, melt the chocolate slowly in a bowl over a pan of hot water. Pour over the cold caramel and leave to set. Cut into squares or bars.