Step 1

In a sauce pan whisk together milk (2cups), egg yolks (and sugar (3/4cup) and salt (1/8tsp). Pour about 1/2 of this mixture into a dish. Into it then add starch (3tbsp) and flour (3tbsp). Whisk well so there are no lumps. Pour flour/starch mixture into the remaining milk mixture into a sauce pan.

Step 2

Cook on medium heat stirring constantly. Custard will gradually thicken.  I find it's best to use a whisk. Once you see bubble to pop, reduce heat to low and simmer for 2-3 minutes.

Step 3

Remove from the heat and strain through a fine mesh sieve. Cover tightly with a plastic wrap and let cool to room temperature.

Step 4

To speed up cooling you can use a cold water bath. Or if you plan on making buttercream next day you can refrigerate covered custard overnight.If refrigerating let custard come to room temperature before mixing with butter.  I like to microwave it on high in 5 second intervals, stirring gently after each heating.

Step 5

Beat room temperature unsalted butter (2cups, 4sticks) for 15 seconds. Then add powdered sugar (1cup, or use more if you prefer sweeter buttercream) and beat on low until fully incorporated into the butter. Increase the speed to medium and beat for 30 seconds.

Step 6

Gradually add room temperature custard to butter, creaming well after each addition.Once fully blended, beat in Vanilla Extract and/or Vanilla Bean Paste.Beat on high for 10 seconds. German buttercream is ready.