Preheat the oven to 180℃ (fan) (or 200℃ conventional) / 350℉.
Grease and line two 20 cm cake tins (I use springform pans).
Mix the flour, baking powder and cocoa powder in a large bowl.
190 g plain flour (all-purpose flour), 1 tsp baking powder, 50 g cocoa powder
Place the butter and light brown sugar in a microwaveable dish. Microwave on high for 1 minute or until melted. Stir well. Allow to cool for a few minutes.
200 g light brown sugar, 125 g butter
Add the milk to the melted butter and sugar mixture and whisk until smooth.
180 ml milk
Pour the liquid mixture into the large bowl with the dry ingredients. Fold together gently.
Then add the beaten egg in thirds, mixing after each addition.
3 eggs
Pour the cake batter into the lined cake tins, splitting the mixture evenly between the tins.
Place the tins in the preheated oven, if you wish on a baking tray to keep them stable.
Bake for 20 to 25 minutes until a cake tester or toothpick comes out clean from the centre.
Remove the tins from the oven, leave to cool for five minutes or so until you can handle them. then push the cakes out of the springform pans by pushing up the base. Remove the base from under the cakes, peel off the baking paper and put them on a cooling rack.
Allow to cool completey.