Step 1 Combine the egg yolks and one-third of the sugar in a bowl and whisk to a light ribbon consistency, about 3 to 4 minutes. Add the flour and whisk it in thoroughly.
Step 2 In a pan, heat the milk with the rest of the sugar and the vanilla bean and seeds. As soon as it comes to a boil, pour it onto the egg yolk mixture a few tablespoons to start, then all of it, stirring as you go. Mix well, then return the mixture to the pan.
Step 3Bring to a boil over medium heat, stirring constantly with the whisk. Allow the mixture to bubble, still stirring, for 2 minutes, then tip it into a bowl.
Step 4To prevent a skin forming, cover tightly with plastic wrap on the surface of the creme. Chill in an ice-water bath, then refrigerate overnight. Can be kept in the refrigerator for up to 3 days. Remove the vanilla bean before using.