|Cocoa||1⁄4 Cup (4 tbs)|
|Sugar||2⁄3 Cup (10.67 tbs)|
|Milk||1 1⁄2 Cup (24 tbs), scalded|
Blend cocoa, sugar, salt and flour in top of double boiler; add milk and place over boiling water, stirring constantly until sauce thickens; then continue to cook for 10 minutes with occasional stirring.
Beat egg thoroughly and stir in a little of the hot mixture; then return to the rest of the hot filling and cook 2 minutes longer, stirring constantly.
Remove from heat, add butter and vanilla, and cool thoroughly, stirring occasionally to prevent the formation of a "skin" on the surface.
Spread between layers of cake.
Enough for two 8 or 9-inch layers.