Wilton's buttercream icing recipe calls for 1/2 cup solid vegetable shortening, 1/2 cup of softened butter or margarine, 1 teaspoon of clear vanilla extract, 4 cups of sifted confectioner's sugar and 2 tablespoons of milk. The recipe is prepared with a hand or stand mixer, in stages.
To begin, beat the butter or margarine with the shortening on high speed until the mix appears light and fluffy, then add the vanilla and beat for one minute. Gradually beat in the sugar, one cup at a time, on medium speed, scraping the sides frequently, until the mixture appears dry. Blend in the milk a tablespoon at a time, continuing on medium speed, until the icing achieves desired consistency. If a thinner icing is needed, add in up to 2 tablespoons of light corn syrup, water or milk at this stage to adjust the thickness of the mix.
An alternate pure white version of this icing recipe instructs the user to omit the butter or margarine and replace it with a 1/2 cup of vegetable shortening, in addition to a 1/2 teaspoon of colorless butter flavoring. The pure white version can also be thinned with up to 4 tablespoons of light corn syrup, water or milk as desired. Cover the bowl of finished icing with a damp cloth until ready to use to prevent drying.