In a medium bowl, whisk egg yolks and sugar until pale yellow. Whisk in corn starch. Set aside.
In a stainless steel saucepan, bring milk and vanilla bean to a boil, remove from heat and remove vanilla bean. Stir a small amount of the hot milk into the egg yolk mixture. Return milk to heat and while constantly stirring with a wooden spoon, slowly add the egg mixture to milk. Mixture will thicken.
Allow to just come to a boil, remove from heat and stir in butter. Put mixture through a sieve into a bowl and cover with plastic wrap (this keeps mixture from forming a skin over top). Cool slightly.
Stir in melted white chocolate, cover and refrigerate until ready to assemble pie. This pastry cream is used in the Elegant White Chocolate Banana Cream Pie.