German Buttercream

Makes 8 cups

4 Egg yolks
1 tsp Vanilla bean paste
3 tbsp Cornstarch
3 tbsp Flour
1 cup Powdered sugar
1/8 tsp Salt
3/4 cup Sugar
1 tsp Vanilla extract
2 cups Butter
2 cups Milk

Note:  Received these details on a baker’s page.  No instructions provided.