Preheat the oven to 160°C. Grease an 1.5L (6-cup) capacity ovenproof baking dish.
Sift the flour, 1/2 cup (110g) sugar and 1/4 cup (25g) cocoa into a bowl and stir to combine. Make a well in the centre. In a separate bowl, whisk melted butter, milk, vanilla extract and egg. Gradually pour into the well, then fold to combine.
Spread mixture evenly into prepared dish. Combine remaining 1/2 cup (110g) sugar and 1/4 cup (25g) cocoa and sprinkle over the top of the pudding. Carefully pour 2 cups (500ml) boiling water over the top of the pudding.
Bake for 30-35 minutes until the top is firm. Stand for 10 minutes to cool slightly.⏱ 35 min
Dust the warm pudding with extra cocoa and serve immediately with vanilla ice cream.