Use this recipe to make our Genoise Layer Cake.
Bring milk, 1/4 cup sugar, the vanilla bean and seeds, and salt to a simmer in a medium saucepan over medium heat.
Whisk egg yolks and remaining 1/4 cup sugar in a medium bowl. Whisk in cornstarch, 1 tablespoon at a time. Ladle 1/2 cup hot milk mixture into yolk mixture, whisking. Add remaining milk mixture, 1/2 cup at a time. Pour mixture into pan; heat, whisking constantly, until mixture comes to a simmer and has thickened, about 2 minutes. Discard vanilla bean.
Transfer mixture to the bowl of an electric mixer fitted with the paddle attachment. Add butter; mix on medium speed until butter has melted and mixture has cooled, about 5 minutes. Remove bowl; place plastic wrap directly on surface to prevent a skin from forming. Refrigerate until cold, at least 2 hours (up to 2 days).