Preheat the oven to 180. First of all whisk the eggs along with the oil and the sugar until creamy and well combined. Add the vanilla essence now along with the milk.
Continue beating with a wire whisk or a hand held electric blender. Sift the flour and the baking powder for two times atleast.
Slowly fold in the dry ingredients into the wet ones and mix well. Take care not to over mix. Now divide this mixture into two parts. Add cocoa powder to one part and keep the other part as it is.
Now comes the assembling part, add the plain batter first in a greased 9" round cake pan. Top it up with the chocolate part. Using a toothpick, make random swirls all over. Bake it for 25 to 30 minutes.
Take care not to open the oven door for the first 20 minutes. Otherwise the cake shrinks. After 30 minutes, insert a skewer to check. Run a knife along the sides of the cake pan and invert it on to a cooling rack. Let it cool completely before slicing.
Serve as desired with tea or coffee.
