300 ml (1 375g tin) condensed milk
500 g white chocolate, roughly chopped
4 tsp instant coffee, dissolved in 2 tsp hot water
100 g walnut halves, optional
Pour the condensed milk and the dissolved coffee into a heatproof bowl that can nestle comfortably in a saucepan. Put a inch or two of hot water in the saucepan, fit the bowl on top and put the whole contraption over low heat. Let the condensed milk warm up a bit, then add the chopped chocolate. Stir well, then watch carefully as the white chocolate starts to melt. Remove it from the heat and stir again. Tip the mixture into a lined tin and smooth the top. Gently press the walnut halves on top - you won't need all of them but it's helpful to have a selection to choose from. Cover loosely with more plastic wrap and put in the fridge to set. Leave for at least two hours if you can. Cut into small squares and store in a lidded (hidden?) container in the fridge.
Source: http://kitchen-maid.blogspot.co.nz/2012/06/sweet-sweet-friday-white-mocha-fudge.html