Preheat oven to 180°C/350°F/Gas Mark 4. Cut the bottom off each pear, just so that they will stand upright. Peel them if desired. Using a melon bailer or apple corer, remove the core and seeds, leaving a space about the size of a large walnut.
Press ricotta through a sieve and mix with ginger, chocolate and icing sugar. Stuff this mixture inside the pears.
Cut four 12 cm (4 ⅔ in) squares of foil or baking paper, and brush one side with melted butter. Sit one pear upright on each square, then brush with remaining butter. Fold the excess foil/paper around pears, then sit in a roasting dish that is just large enough to hold them upright.
Pour wine over and bake 45-60 minutes, until a skewer poked into the thickest part of the ‘neck’ passes through easily. Leave to cool for 10 minutes before attempting to remove the foil, then pour reduced wine over and serve.