In a large mixing bowl, use an electric mixer with a paddle attachment to beat the softened butter on medium speed for about 2-3 minutes. It needs to become creamy and light in color.

Add the sifted icing sugar to the butter gradually. Starting the mixer on low speed and once the sugar is mostly incorporated, increase the speed to medium and beat until fully combined.

Pour in the vanilla extract and 3 tablespoons of heavy cream. Whip on medium-high speed for about 3 more minutes, until the frosting is light and has a cloud-like texture. Don't forget to stop the mixer and scrape down the sides of the bowl with a spatula a couple of times.

Check the consistency of your frosting. If it's too thick, add more heavy cream, one tablespoon at a time, beating well after each addition. If it's too thin, you can add a little more sifted icing sugar until it thickens up.