Mix sugar and water and let it come to boil.
When the syrup reaches 230°F, start whisking eggs.
Beat egg whites until frothy.
Add the powdered sugar little by little and beat.
Keep on beating until it reaches stiff peaks. Still the mixture should be shiny. Do not over beat at this stage.
When the sugar syrup comes to 245°F, remove from stove and add it to the egg whites in a continuous stream while beating the egg whites.
When all the syrup is incorporated, beat the mixture until the bowl is cool to touch. It may take 10 minutes at this stage.
Once the bowl is completely cool, start adding butter cubes one at a time.
Beat until mixed thoroughly before adding the next cube.
Once all the butter is mixed keep on beating until the mixture turns to batter consistency.
Add vanilla essence and continue beating. The mixture may look like curdled but keep on beating.
After a while the mixture will turn into fluffy butter cream.
Cover the bowl with a cling wrap until ready to use it on cake.