Here is the recipe i used.
100g butter 10 fl oz full fat milk
800g soft brown sugar 1 tsp vanilla extract
Grease a shallow 18-cm square tin. Place the milk, sugar and butter into a large saucepan and bring slowly to the boil, stirring constantly, until the butter has melted. Bring to the boil, then cover the pan with a lid and simmer for 2 minutes. Uncover and continue to boil, stirring occasionally, until a little of the mixture, dropped into a small bowl of cold water, forms a soft ball when rolled between your fingers. The temperature on a sugar thermometer should reach 116c. Remove from the heat and stir in the vanilla extract. Leave to cool for 5 minutes.
Use a wooden spoon, beat the fudge until it begins to lose its shine and is thick and creamy. Immediately turn the mixture into the tin and leave to cool. When cool, mark the surface into 2.5cm squares and leave until set.
(recipe courtesy of 1001 Cupcakes, cookies and other tempting treats by Susanna Tee)