This is a Martha Stewart recipe for a whipped buttercream frosting for wedding cakes - perhaps this might work.

MarthaStewart's:Cooked sugar frosting


Grand Marnier Italian Meringue Buttercream

2 c sugar
2/3 c water
6 egg whites
pinch of salt
1/4 t cream of tartar
1 1/4 pound unsalted butter, at room temperature
1 t vanilla
3 T Grand Marnier or other orange flavored liqueur eg cointreau

Combine sugar and water in a heavy saucepan and bring to boil without
stirring. Cover and let boil until the sugar is completely dissolved, 3-5
minutes. Uncover and let the mixture boil until it reaches the soft ball
stage, 240 on a candy thermometer.

while the syrup is cooking, beat the egg whites with the salt and cream of
tartar until very stiff peaks form.

When the syrup reaches 240, pour 1/4 c of the syrup into the stiffly beaten
egg whites, drop by drop, beating at high speed. Gradually add the rest of
the syrup in a fine stream and beat for 8-12 minutes, or until the mixture
is cool. There must be no heat left in the meringue or the butter will melt.

In a separate bowl, cream the butter until light and fluffy. Add the butter
to the cooled meringue mixture, 3 T at a time, beating well after each
addition. The frosting should gradually become very thick and creamy. If it
does not thicken properly, the meringue may have been too warm; stir over a
bowl of ice until the frosting thickens. Beat in the vanilla and the Grand
Marnier. The buttercream should be used immediately. Keep the buttercream
cool over a bowl of ice water, stirring often, but do not refrigerate it.
Frost each layer with an undercoat and refrigerate immediately.