1. Lightly oil a small rectangular foil dish.
2. Put the butter into a 2.8 litre (5 pint) ovenproof glass bowl and microwave on HIGH for 30 seconds, or until the butter is only just melted.
3. Stir in the sugar, milk, 60 ml (4 tbsp) water and the vanilla flavouring and continue stirring for 1 minute until the sugar is almost dissolved. Microwave on HIGH for 2 minutes, then, using oven gloves, give the bowl a gentle shake.
4. Microwave on HIGH for 6 minutes or until a spoonful of the mixture forms a soft ball when dropped into cold water.
5. Carefully remove the bowl from the oven, add the raisins and chopped cherries and beat constantly until the mixture is thick and creamy and tiny crystals form. (Do not continue beating after this or the fudge will become candy-like and granular.)
6. Immediately pour the fudge into the prepared dish. Allow it to cool, then refrigerate it overnight before turning it out and cutting it into squares.