Beat butter and sugar till light and fluffy. Add one egg at a time beating in between to form peaks. Add vanilla essence and oil. Sieve flour and baking powder in a separate bowl. Add 3 tbsp of flour mixture to the butter at a time while continuing to mix till you are done with all the flour. Pour batter into any shape greased mould and bake in a pre heated oven at 180C till done. Let it cool a bit remove on ramekins and cut in half horizontally