In the bowl of a stand mixer fitted with the paddle attachment, beat butter at medium speed until smooth, about 1 minute. Add cream cheese, and beat until smooth and combined, stopping to scrape sides of bowl. With mixer on low speed, gradually add confectioners’ sugar, beating until just combined. Beat in vanilla; increase mixer speed to medium, and beat until light and fluffy, about 30 seconds.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/apple-cider-whoopie-pies/