01 -
Set your oven to 170C/335F (regular) or 150C/305F (fan/convection). Coat a 5–6 cup baking dish with a little butter.
02 -
Stir together cocoa and brown sugar in a bowl, then leave it aside for later.
03 -
Combine flour, cocoa powder, sugar, baking powder, and salt with a whisk in a large bowl.
04 -
Mix melted butter and milk in a jug, then whisk in vanilla and the egg until smooth.
05 -
Pour the wet mix into your bowl of dry ingredients. Stir everything together until it makes a thick, smooth batter. Evenly spread it into the prepared dish.
06 -
Evenly scatter the cocoa-sugar blend onto the batter. Make sure to distribute it gently with a little shake.
07 -
Using the back of a dessert spoon, slowly drip boiling water over the dish. This keeps the top smooth.
08 -
Pop it in the oven for about 30 minutes. The cake is ready when it springs back if you lightly press the top. The surface will have a crackly, brownie-like finish.
09 -
Take it out and let it rest for just a couple of minutes. Serve it warm right away to enjoy the gooey sauce underneath.