01 -
Warm up oven to 175°C. Coat pan with butter and add parchment. Combine flour, baking powder, baking soda, and salt through a sieve. In another bowl, whip butter and sugar till light. Drop in eggs one by one, stirring well each time. Add vanilla. Switch between adding dry stuff and milk to the butter mix, starting and finishing with dry stuff.
02 -
Split the mix in two equal parts. For one half, stir hot water into cocoa until smooth, then mix into that half until fully blended.
03 -
Drop spoonfuls of white and brown batter into your pan, switching between them. Drag a knife through just once or twice to get swirls without mixing too much.
04 -
Put in oven for 50 minutes or until you can stick a toothpick in and it comes out dry. Let it sit in the pan for 10 minutes before moving to a rack to cool all the way.