Preheat the oven to 190°C.
Place the chocolate in a heatproof bowl. Bring the cream to the boil in a saucepan set over a moderate heat. Remove from the heat and pour over the chocolate, stirring well until smooth. Add the cornflour and whisk until combined.
Pour into a shallow, ceramic baking dish and allow to cool to one side for 10 minutes.
Prepare the crumble topping by placing the butter, sugar and flour in a food processor. Pulse until the mixture resembles breadcrumbs. Spoon on top of the chocolate filling and bake for 20-25 minutes until the crumble topping is golden in colour and cooked.
Remove from the oven and allow to cool for 5-10 minutes to one side. Dust with icing sugar before serving.
*This pudding is very rich and indulgent so it shouldn't be eaten too often. But it's perfect for those special occasions!