First of all, Heat the sugar and egg whites in a bowl. Stir the mixture for 5 minutes, or until it is completely dissolved. The mixture should feel smooth between your fingers. If you’re using a hand mixer, pour the egg whites and sugar mixture into a bowl.
Mix the egg white and sugar mixture on low speed until it becomes opaque. Use the whisk attachment to beat the mixture. After this, Increase the speed to medium-high and continue beating for approximately 10 minutes, or until the meringue reaches stiff peak standing and is at room temp. The mixer should be on low.
Add the butter one tablespoon at a while, stopping when it is completely incorporated before adding the next. Mix in the vanilla essence. Now Scrape the bowl down to ensure everything is well combined.
Continue mixing until the buttercream is smooth. You can place the buttercream in the refrigerator for up to 15 minutes before you start mixing it again.