Separate the egg whites,add in sugar and (using a double boiling method)place the bowl on top of hot water keep stirring you must be patient till all the sugar granules melt..ensure the egg whites doesn't cook

Once the sugar granules melt transfer the liquid in a stand mixer or using the hand mixer..mix until soft peaks starts to form then add your butter bit by but (cubes) until the buttercream firms up then add essence and salt.