1. Heat the milk with vanilla bean in a heavy saucepan until scalded. Set aside.
2. Blend the egg yolks and sugar in the top of a double boiler. Remove vanilla bean from milk and gradually add the milk to egg yolk mixture, stirring constantly.
3. Cook and stir over boiling water until mixture coats a metal spoon; do not overcook. Remove from boiling water and cool to lukewarm over cold water. Blend in the kirsch.
4. Refrigerate until ready to serve.