Preheat oven to 180°C. Grease a small baking dish (15cm) or 4 ramekins.
Whisk together pudding mix, ¼ cup milk, egg and 75g melted butter. Transfer to baking dish/ramekins.
Place brown sugar, 25g butter and ¾ cup water in a small pot and bring to the boil, whisking until combined. Slowly and carefully pour mixture on top of pudding batter.
Bake for about 25 minutes, until cake is cooked and bounces back when pressed.