Leave stems on peeled pears. Sprinkle with lemon juice to prevent browning. Set aside.
In a saucepan large enough to accommodate 4 pears standing upright, combine water and sugar. Place over medium heat and boil until sugar is dissolved. Stir in vanilla, then place the pears in. Reduce heat, cover and simmer for 15 minutes. Allow to cool in liquid, then drain.
In the top of a double boiler, combine chocolate, cream and butter. Heat, stirring, until chocolate is melted and smooth. Remove from heat and stir in coffee liqueur.
Place pears on serving dish, pour chocolate sauce over pears, and garnish with maraschino cherries.