1. In a medium saucepan, combine the milk, 1/4 cup sugar, vanilla bean and seeds, and salt. Cook over medium heat until mixture comes to a simmer.

2. In a medium bowl, whisk together the egg yolks, cornstarch, and remaining 2 tablespoons sugar. Whisking constantly, slowly pour about 1/2 cup of the hot-milk mixture into the egg-yolk mixture. Continue adding milk mixture 1/2 cup at a time, until it has been incorporated. Pour mixture back into saucepan, and cook over medium heat, whisking constantly, until it thickens and registers 160 degrees on an instant-read thermometer, about 2 minutes. Remove and discard vanilla bean.

3. Add the butter, and mix until the butter melts and the mixture cools, about 5 minutes. Place pot in an ice-water bath until mixture is cooled.

4. Cover with plastic wrap, pressing it directly onto the surface of the pastry cream to prevent a skin from forming. Refrigerate until chilled, at least 2 hours or up to 2 days. Just before using, beat on low speed until smooth (you can also whisk by hand).