Line a 8" square tin with baking paper, I like to grease the tin with some butter first to help the baking paper stick to it
In a large heavy bottomed pan heat the condensed milk, semi skimmed milk, butter, granulated sugar, and golden caster sugar on a low heat until all the sugar is dissolved and the mixture is smooth
Then turn up the heat and let the fudge boil for 10 minutes. Keep stirring during this time
Take off the heat and beat the fudge until it starts to set, then pour into the tin
Sprinkle your desired amount of sea salt over the top of the fudge
Leave the fudge for several hours or overnight to set, you can set it in the fridge quicker, then cut up into pieces to serve
Store in an airtight container in the fridge for up to 3 weeks