Ingredients
1/4 cup unbleached all-purpose flour
1 cup whole milk
1 teaspoon pure vanilla extract
Pinch of kosher salt
2 sticks unsalted butter, room temperature
1 cup sugar
1 vanilla bean, split and seeds scraped
Preparation
In a small saucepan, whisk together flour, milk, vanilla extract, and salt until smooth. Heat over medium-high, whisking constantly, until mixture becomes thick and resembles pudding, 3 to 4 minutes. Remove from heat; transfer to a bowl. Cover surface with plastic wrap and let cool completely, about 30 minutes.
In a stand mixer fitted with the paddle attachment, beat butter with sugar and vanilla seeds on medium speed, scraping down sides as necessary, until light and fluffy, about 2 minutes. Add milk mixture and continue to beat until frosting is light and fluffy and looks like whipped cream, 2 to 3 minutes. Use immediately.
