Microwave Condensed Milk Fudge

Combine butter and castor sugar in a microwave safe bowl. Add condensed milk – do not stir. Microwave on high for about 10 minutes (stopping every minute to stir – so 10xtimes in total) or until golden brown. Allow to cool slightly and beat with a wooden spoon until the fudge starts to set. Pour into a square tin lined with baking paper and allow to set before cutting into squares.