Now get two mixing bowl.
Get ur egg and separate d the egg white from d yolk and put in diff bowl

Goto the bowl wit egg yolk pour sugar,Milk,Oil and vanilla den stir well wit a wishk or spoon
Wen they mix well add ur flour and mix well

Den go back to ur egg white beat it very well with a wishk or hand mixer den add ur tarter and continou beating 4 five minites den add sugar and continue beating until it turns creamy if not continou add sugar and beat.

Once it is creamy collect ur cake barter 4rm 1st bowl nd pour in creamed egg white mix wit a spoon nd divide d mixture into two add cocoa in 1 bowl nd mix

Bake separately for 45 minutes and allow ur cake to cool

Slice d cake in desired size
Get ur butter cream spread on 1st vanilla cake layer nd place chocolate cake ontop,den vanilla cake again