Drain the cherries in a sieve over a bowl. Cut them in half. Peel the pear, then grate it coarsely.
In a large bowl, combine the cherries, pear, the raisins, sultanas and brandy. Stir well and cover with clingfilm.
Heat in the microwave on high for 3 mins, then leave to cool for 5 mins to let the fruit plump up. Break the chocolate into squares while you wait.
Tip the chocolate and butter into the hot fruit. Stir, then leave to melt. Let it cool, uncovered, for about 15 mins.
Meanwhile, rub 1 tbsp butter around the inside of a 1-litre pudding basin.
Lay two sheets of foil over each other and butter the one on top. Holding both sheets together, fold a 3cm pleat across the middle of the foil and set aside.
Beat the eggs together in a small bowl. Sift the flour, sugar, mixed spice and cocoa powder on top of the chocolatey fruit, then add the breadcrumbs, eggs and 1 /4 tsp salt.
Stir everything together with a wooden spoon – it will be quite a wet mixture. Tip it into the buttered basin.
Cover the pudding with the buttered foil (buttery-side down), and scrunch it over the edge of the basin. Tie string tightly under the lip of the basin, and make a string handle to help you lower the basin in and out of the saucepan later.
Trim the foil so that a frill of about 5cm is left sticking out, then tuck the frill up and under itself neatly. The aim is to keep the pudding watertight beneath.
Put a heatproof saucer into the very large saucepan, then put the basin on top. Pour in just-boiled water to come halfway up the basin.
Cover the pan and steam the pudding for 21 /2 hrs. Test the pudding is cooked by inserting a skewer through the foil – if there is any wet mixture, steam for 15 mins more then check again.The pan should be simmering rather than boiling hard. Top up the water levels as it cooks, if you need to.
To store, let the pudding cool and leave in a cool dark place to mature. Don’t unwrap the foil.
To reheat, steam in a pan for 30 mins, or microwave on medium for 5 mins. Remove the foil to microwave, covering with clingfilm instead.
For the sauce, break the chocolate into squares. Put all the ingredients in a small pan and heat gently, stirring, until smooth. Serve the pudding topped with any remaining cherries, the sauce and a dollop of double cream.