Ensure your butter is at room temperature and add it to your stand mixer. Add in your icing sugar and your vanilla.
If your stand mixer has a guard, make sure this is on because there will be a cloud of icing sugar erupting and descending on you and everything in your lovely kitchen.
Turn your mixer onto it’s lowest speed and mix until everything starts coming together. You will know this is happening because the mixer will sound as if it’s starting to struggle a bit.
Once everything is just combined, turn the mixer up onto medium speed and beat for 7-8 minutes more. You may want to scrape everything down half way through to ensure there is no unmixed butter or icing sugar sitting at the bottom of the bowl.
After the 8 minutes you should be left with a bowl of the fluffiest white, most delicious buttercream. You can use it in cakes and on cupcakes straight away.
Buttercream can be stored in your fridge for as long as the date on your butter, or it can be frozen if you wrap it well and keep it in freezer bags.