Start by preparing the butter; press a whisk into it to check if it's soft enough. If it yields easily with a little pressure, it's ready to use.
Beat the butter on high speed for about two to three minutes until it becomes lighter in color and texture.
Gradually add the powdered sugar, vanilla extract, and salt to the butter, mixing on medium-high speed for another two to three minutes.
Incorporate the sweetened condensed milk in three separate additions, mixing for one full minute after each addition.
After all the milk is added, increase the speed to high and mix for an additional minute to ensure proper emulsification with the butter.
Change to the paddle attachment and mix on low speed for a few minutes to achieve a smooth consistency.
Taste the frosting and adjust the flavor with more vanilla or salt if necessary.
