Preheat your oven to 350°F (175°C) and lightly grease an 8-inch baking dish. This prevents sticking and ensures the pudding can be served easily after baking.

In a mixing bowl, whisk together the flour, cocoa powder, baking powder, and sugar. Add the milk, melted butter, and vanilla extract, then stir until a smooth batter forms without overmixing.

Spread the chocolate batter evenly into the prepared baking dish. Use a spatula to smooth the surface so the pudding bakes evenly.

In a small bowl, combine the brown sugar and cocoa powder. Sprinkle this mixture evenly over the batter, covering the entire surface.

Carefully pour the hot water over the back of a spoon onto the pudding. Do not stir, as the water needs to remain on top to create the self-saucing effect during baking.

Bake for 30–35 minutes until the top is firm and cake-like. Allow the pudding to rest for a few minutes before serving warm, making sure to scoop down into the rich chocolate sauce underneath.