Melt white chocolate according to package instructions. Let cool slightly.
In a medium mixing bowl, combine butter, confectioners’ sugar, salt, vanilla, and milk. Beat at medium speed with a mixer until smooth and creamy. Add melted white chocolate, and beat at high speed until mixture is light and fluffy.
Use immediately, or transfer buttercream to an airtight container, and refrigerate until needed. Let come to room temperature before using.
Recipe by TeaTime Magazine at https://teatimemagazine.com/white-chocolate-macarons-recipe/