1. Line an 8-inch square pan with butter/parchment paper. 2. In a saucepan, add sweetened condensed milk, brown sugar, and, butter.
3. Place on medium heat and stir together until the sugar is dissolved and the mixture simmers and starts to thicken.
4. Reduce the heat to low and stir in all the white chocolate.
5. Pour the fudge into the prepared tin. Smooth the top and sprinkle salt all over the top.
6. Place in the fridge for 3-4 hours to set or even better, overnight. Cut into thick squares to serve. Store fudge in the fridge.