German Buttercream (Whipped Vanilla Custard Frosting) Recipe
Return milk to a simmer and discard vanilla bean after scraping out the flavorful seeds and pulp inside (or remove other flavoring elements, and scrape them as best you can, if possible). Ladle 1/2 cup hot milk into the eggs and whisk to combine. Repeat with two more 1/2-cup additions, then pour the warmed eggs into the pot. Cook over medium heat, whisking constantly, until the custard turns thick and lumpy, about 3 minutes (the timing can vary depending on the specifics of your stove and cooking vessel, so adjust the heat accordingly if it seems to move too slow). As soon as the custard begins to bubble, set a timer and continue cooking and whisking for exactly 2 minutes longer. This helps neutralize a starch-dissolving protein found in egg yolks.