After 2 times of baking butter cake with a not so satisfied result (1st too dense, 2nd time too dry, haiz), i made a 3rd attempt this time and i’m very very pleased with the result. even the marble cake swirls nicely this time. :)
Found the recipe from here. She has very good recipes and i will definitely refer to her blog again next time.
I took a small portion of the batter to mix with cocoa powder. In order to make it swirls nicely, you just have to scoop a spoonful of the chocolate mixture into the baking tray followed by the plain one on top, repeating the process layer by layer. No stirring is required.