Rachel Allen's Fudge

375g condensed Milk
450g golden caster sugar
100g butter
1tsp vanilla essence (if required or 75g of chocolate chips)

1. melt the butter then add milk and sugar, cook for 10 to 15mins on a high heat (soft crack on jam thermometer)
2. fill the sink with some water and place this pan on and mix this mixture with some minutes.  this will make the mixture hard quickly.  when grainy, its time to put into a baking tray.
3. then put this mixture on the tin and spread out about 1cm think.
4. let it cool for about 5 minutes and you have to cut the shape within 3 to 5 minutes otherwise this mixture will very hard.