Beat Butter: In a large mixing bowl using electric hand beaters or a stand mixer with the paddle or whisk attached, beat the softened butter for 2 minutes until pale and creamy.
Add Sugar Gradually: Gradually add powdered sugar, one cup at a time, beating well (about 15 seconds) after each addition.
Add Cream and Vanilla: Add heavy cream and vanilla extract, then beat for 2-3 minutes until the frosting is light and fluffy.
Adjust Consistency: Check the consistency of your buttercream. If it's too stiff, add a little more cream, a tablespoon at a time, until you achieve the desired consistency. If it's too soft, add more powdered sugar, a few tablespoons at a time, until it firms up.
Final Whip: Once the consistency is just right, give the buttercream one final whip for about 30 seconds to make sure it's perfectly smooth and airy.
Ready to Use or Store: Your buttercream is now ready to use for decorating cakes, cupcakes, or any dessert. If not using immediately, store it in an airtight container in the refrigerator. When ready to use, let it come to room temperature and rewhip briefly to bring back its creamy texture.