Mix Base Ingredients: In a large mixing bowl or stand mixer with the paddle attachment, combine the powdered sugar, pasteurized egg whites, salt, and vanilla. Start mixing on low speed to incorporate the ingredients without creating a powdered sugar cloud, then increase to medium-high speed. Beat for about 5 minutes, or until the mixture is smooth and slightly fluffy.

Add Butter Gradually: With the mixer still running, slowly add the softened butter, a few pieces at a time. Allow each addition to fully incorporate before adding more. Continue until all the butter is added, and the buttercream is creamy and smooth.

Add Food Coloring: Add a single drop of purple/violet food coloring to neutralize any yellow tones from the butter. Be cautious to only use a small amount; too much can cause the buttercream to appear gray or purple.

Whip on High Speed: Increase the mixer speed to high and whip for 10 minutes. This step gives the buttercream a light, fluffy texture. The mixture should look airy and smooth by the end. Taste the buttercream and adjust based on preference. Add more sugar, salt, or vanilla extract if desired.

Smooth on Low Speed (Optional): For a super-smooth finish ideal for frosting, reduce the speed to low and mix for an additional 10 minutes. This will remove any air bubbles, creating a smooth buttercream. If you plan to pipe decorations, you may skip this step to keep the buttercream firmer.