Step 1
Split 1 vanilla bean in half, scrape the seeds out into a small dish, and put the pod in a medium, heavy-bottom saucepan. Add 1 cup (240 g) whole milk and 1 cup (240 g) heavy cream and heat over medium-low heat until just about to simmer. Remove from the heat, cover the pan, and set aside.
Step 2
In the bowl of a stand mixer fitted with the paddle attachment, beat 5 egg yolks, at room temperature on low speed until combined. Slowly add 1¼ cups (250 g) granulated sugar, followed by ¼ tsp. salt and vanilla bean seeds. Increase the mixer speed to medium-high and beat the egg mixture until very thick and pale yellow, about 5 minutes. Scrape down the sides of the bowl, lower the mixer speed to low, and beat in ¼ cup (35 g) cornstarch.
Step 3
Pour the hot milk mixture into a medium liquid measuring cup, leaving the vanilla bean pod behind in the pan. With the mixer still on low speed, very slowly add the hot mixture, beating until completely incorporated. Transfer the mixture to the saucepan and cook over medium-low heat, stirring constantly with a wooden spoon, until the pastry cream becomes very thick and begins to boil, 5–7 minutes. Switch to a whisk and whisk the pastry cream until glossy and smooth, 3–4 minutes. Remove from the heat and strain the pastry cream through a fine-mesh sieve into a medium heatproof bowl. Stir in 2 tsp. pure vanilla extract and 1 Tbsp unsalted butter.
Step 4
Lay a sheet of plastic wrap directly on the surface of the pastry cream to keep it from forming a skin and refrigerate until well chilled.
Step 5
Scrape chilled pastry cream into the bowl of a stand mixer and add 1 cup (2 sticks; 227 g) unsalted butter, room-temperature. Beat on medium-high speed until incorporated.
Do ahead: The pastry cream will keep, with a piece of plastic wrap or wax paper pressed onto its surface and stored in an airtight container in the refrigerator for up to 5 days.
Editor’s note: This German buttercream recipe first appeared on Epicurious in May 2023. Explore the wide world of buttercream with our recipes for American-style buttercream frosting, French buttercream, Swiss meringue buttercream, and Italian meringue buttercream →