This icing is similar, my mom always made it with butter cake - we loved it as kids, I just found it in her recipe box and I'm making it tomorrow for my husband's BD cake. As follows:

MOM'S FLUFF ICING

3 tbsp flour
1 cup of milk
1 tsp vanilla
7 tbsp Crisco
7 tbsp butter, softened
1 1/4 cup powered sugar

Place flour in saucepan. Gradually add milk. Cook, while stirring, until thickened. Add vanilla. Let cool in frig.

Combine Crisco, butter and powdered sugar. Beat 10 minutes. Add cooled flour mixture and beat well.