Set a timer on 7 minutes and pour the egg whites into the kitchen mixer with the whisk attachment.
Put the sugar and water into a pan and bring it to a boil on medium-high and then start the timer.
When the sugar syrup has been boiling for 5 minutes, start the kitchen mixer on full speed and whisk the egg whites for the remaining 2 minutes. When the timer is up the sugar syrup is done about (240 degrees).
With the mixer still going on high speed slowly pour the hot sugar syrup down the side of the mixing bowl.
When all sugar syrup has been added it should look really set up, thick and full. Switch to paddle attachment to incorporate air. Set the timer for 10 minutes and beat on high speed. After 10 minutes you should have a lovely thick meringue.
Add the butter. Start the mixer on high speed and with a butter knife, cut pieces of the butter and add it to the meringue. When all the butter is added it won’t take long for the mixture to turn into nice smooth buttercream. This will take a few minutes, be patient as it will turn into a smooth creamy finish.
After the butter is combined, slow down the mixer and add the vanilla extract. Stop the mixer and scrape down the sides of the bowl with a spatula and start the mixer again to make sure it’s well mixed.