CARTHUSIAN MONKS are well known for producing strong liqueurs, including the famous green variety made by the Grand Chartreuse in France.  Now their brother monks in Slovenia are hoping to expand the market for their own unique aperitif.  The Carthusian Charterhouse monastery at Pleterje in the foothills of the Gorjanci mountains in Slovenia have for some 60 years produced a very special pear brandy. The clear, crisp spirit with a pear inside the bottle is being marketed in the UK for the first time with a price tag of £60. The nine-strong community, assisted by nine lay workers, make the brandy using fruit from the monastery’s orchards. They place glass bottles over tiny Williams pears while they are still on the tree, and the fruit grows to maturity within the bo