Prepare Ingredients: Ensure that the butter is softened to room temperature. Sift the powdered sugar to remove any lumps. Measure out the vanilla extract, heavy cream or milk, and any optional flavorings.
Cream the Butter: In a large mixing bowl, beat the softened butter using an electric mixer on medium speed until it is creamy and smooth. This usually takes about 2-3 minutes.
Add Powdered Sugar: Gradually add the sifted powdered sugar to the creamed butter, one cup at a time, while continuing to mix on low speed. Scrape down the sides of the bowl with a spatula as needed to ensure thorough mixing.
Incorporate Vanilla and Liquid: Once all the powdered sugar is incorporated and the mixture is smooth, add the vanilla extract and mix until combined. Then, slowly add the heavy cream or milk, one tablespoon at a time, until the frosting reaches your desired consistency. Beat on medium-high speed for 2-3 minutes until the frosting is light and fluffy.
Adjust Consistency: If the frosting is too thick, add more heavy cream or milk, a teaspoon at a time, until you reach the desired consistency. If it's too thin, add more powdered sugar, a tablespoon at a time, until it thickens.
Optional Flavorings: If you're using optional flavorings like salt, lemon juice/zest, or almond extract, add them to the frosting at this stage and mix until well combined.
Final Adjustments: Taste the frosting and adjust the sweetness or flavorings as desired. Add more powdered sugar if it's not sweet enough, or more flavorings for additional taste.