Instructions

1. In a medium pot, bring the milk and vanilla bean seed pods to a simmer. Remove from heat and let stand one hour.
2. After and hour, remove the vanilla bean seed pods and return the milk to a simmer.
3. In a medium bowl, whisk the sugar, cornstarch, whole eggs and egg yolks together.
4. Whisk about half a cup of hot milk into the egg mixture to temper it. Pour the egg and milk mixture back into the simmering milk, whisking constantly. Once it begins to thicken and bubble, whisk constantly for a full minute more. The texture should resemble vanilla pudding. Pour the custard into a large mixing bowl, cover with plastic wrap touching the surface of the custard and refrigerate overnight.
5. In a stand mixer fitted with the whisk attachment, whip the custard on medium speed until it is smooth and creamy. Add the room temperature butter a tablespoon at a time until it is all incorporated. You made need to scrape down the sides of the mixer and the beater with a spatula a few times to get everything mixed properly. Then add the salt and whip to combine.
6. Once the butter is all added and the mixture is smooth and creamy, add the cookie butter and whisk to combine.
7. Before using to frost a cake, refrigerate one hour as this buttercream is a little bit loose.