This is the recipe I used for the frosting that I had with the chocolate cake.
1 c. milk3 tbsp. flour
Make a white sauce of above. It will be very thick. Boil for 1 minute while whisking rapidly to mix. Cool completely (I didn't and it was fine)
1/2 lb. (2 sticks) butter
1 c. granulated sugar
2 tsp. vanilla
Cream butter. Add sugar and vanilla. Combine white sauce and beat at high speed on food mixer (or with a whisk) for about 5 minutes.
It was still pretty runny after it cooled, so I added quite a bit of flour to thicken it.
This was good enough to eat alone (and I did).