Vanilla Pastry Cream
In a medium saucepan over medium heat, whisk together the first 6 ingredients, adding them to the pan in the order listed. Cook until bubbly (about 10 min.), stirring regularly at first, then constantly for the last 5 min. Continue to cook and whisk until boiling (about 2 min. more). Whisk the entire bottom of the pan (including the corners) constantly to avoid scorching and to prevent lumps. Boil 1 min.; remove from heat. Remove vanilla bean; whisk in butter. Transfer to a heatproof bowl; cover with plastic wrap touching the surface of the pastry cream. Chill completely in the refrigerator.