This is a recipe from the back of a Hershey's cocoa box from a million years ago, maybe as many as 40 years ago when I was a young wife and mother.
Hershey's Likety-Split Chocolate Frosting
3 cups powdered sugar
1/2 cup cocoa
1/8 teaspoon salt
6 Tablespoons milk
2 teaspoons vanilla
1/3 cup butter, softened
Combine sugar, cocoa and salt in a large mixing bowl. Add milk and vanilla. Mix well until smooth. Add butter and beat until spreading consistency.
Makes about 2 cups frosting enough for an 8"-9" layer cake.