Line a 22cm baking tray with non stick baking paper. Place the butter and milk in a saucepan over low heat, stirring occasionally until butter is melted. Finely crush half of the biscuits in a food processor and crush the remaining ones into small pieces. Place the biscuits, dried apricots, white chocolate, sultanas, coconuts and pistachios in a large bowl. Stir in the milk-butter mixture until all the ingredients are well combined. Press the obtained mixture into the prepared tray. Spread with the melted milk chocolate. Allow to set in a refrigerator for at least 2 hours before slicing into desired slices.