High Humidity Buttercream Icing - cooking recipe

Ingredients

1/4 cup shortening
1/4 cup butter (at room temperature)
1/2 cup palm oil based margarine (the kind that does not require refridgeration)
4 cups icing sugar, sifted
2 tablespoons cornstarch
2 tablespoons cream
2 teaspoons vanilla extract
1 teaspoon lemon juice
2 tablespoons meringue powder

Preparation

In a large bowl, beat shortening butter and margarine till light and fluffy (about 10-15 minutes).
Add icing sugar one cup at a time,beating well after each addition.
Combine corn starch and cream. Add to mixture and beat well.
Add vanilla extract and lemon. Beat well.
Add meringue powder. Beat well.
Thin with a little more cream if too thick, to desired consistency.