After doing some research on this type of frosting, I found that this goes by a crazy amount of "Frosting" names including: Boiled Milk, Heritage , Ermine, Cloudburst, Gravy, Roux, and Cooked Flour Frosting.
Slowly, add a couple tablespoons of milk, whisking until you have a smooth mixture.
Add remaining milk, whisking until smooth and completely incorporated.
Slowly, add a couple tablespoons of milk, whisking until you have a smooth mixture.