Preheat Oven & Prepare Dish: Preheat your oven to 180°C (160°C fan/Gas Mark 4). Lightly grease a 20x20cm (or similar sized) ovenproof dish. You want to ensure the pudding doesn't stick, so a quick wipe with a little oil or butter is key.

Combine Dry Ingredients: In a large mixing bowl, whisk together the plain flour, 50g cocoa powder, caster sugar, baking powder, and salt. Give it a good whisk until the mixture is uniform and there are no visible lumps of baking powder; this ensures even rising and texture.

Combine Wet Ingredients: In a separate smaller bowl, whisk together the milk, vegetable oil, vanilla extract, and the egg. Whisk until everything is smoothly combined and the mixture looks pale yellow and slightly frothy.

Combine Wet and Dry: Pour the wet ingredients into the dry ingredients. Mix with a wooden spoon or spatula until just combined. Be careful not to overmix; a few small lumps are perfectly fine and will disappear during baking. Fold in the chocolate chips. The batter will be thick and glossy, with the chocolate chips distributed throughout.

Prepare the Topping: Pour the batter into your prepared ovenproof dish, spreading it evenly. In a small bowl, combine the light brown sugar and the remaining 2 tablespoons of cocoa powder. Sprinkle this mixture evenly over the top of the batter. It will look like a dark, sugary dust sitting on top of the chocolate batter.

Add Hot Water: Carefully pour the 360ml of hot water over the brown sugar and cocoa layer. Do not stir! The water will sit on top, creating a thin, dark liquid layer. This is the magic step that creates the delicious fudge sauce underneath the cake as it bakes.

Bake: Place the dish in the preheated oven and bake for 25-30 minutes. You'll know it's ready when the top cake layer is set and springs back slightly when gently touched, and the edges are bubbling with a rich, dark sauce. The kitchen will be filled with a wonderful, deep chocolate aroma.

Serve: Carefully remove the pudding from the oven. The sauce underneath will be incredibly hot and molten. Serve immediately with a dollop of clotted cream or a scoop of vanilla ice cream. The contrast between the warm, fudgy cake and the cool topping is simply divine.