2½ sticks unsalted butter, softened
1 vanilla bean, halved lengthwise
2½ cups confectioners' sugar (10 ounces)
1 teaspoon vanilla extract
2 Tablespoons heavy cream
1. In a standing mixer fitted with the whisk attachment, beat the butter at medium-high speed until smooth, about 20 seconds. Using a paring knife, scrape seeds from vanilla bean into butter and beat mixture at medium-high speed to combine, about 15 seconds.
2. Add confectioners' sugar and salt; beat at medium-low speed until most of the sugar is moistened, about 1 minute. Scrape down the bowl and beat at medium speed until mixture is fully incorporated, about 30 seconds; scrape bowl, add vanilla and heavy cream, and beat at medium speed until incorporated, about 20 seconds, then increase speed to medium-high and beat until light and fluffy, about 4 minutes, scraping down bowl once or twice.