I have a buttercream recipe that calls for egg whites, powder sugar, & salt to be whipped to stiff peaks over a double boiler before being added to the other mixture. My 2 questions are :

#1..can I substitute Meringue powder for the egg whites and then not have to use the double boiler.

or
#2 can I just use a stainless steel bowl over a pot of boiling water and whip it that way?

thanks in advance!

The recipe you have is for Italian Meringue Buttercream. If you sub meringue powder, you won't get the right consistency. It is not difficult to make, just follow the directions and use a thermometer.

I don't know the answer to the first question, but yes you can use a metal bowl on a pot of boiling water.

Are you wanting not to cook at all, or not to cook in a double boiler?

You need to cook the sugar for meringue buttercream.

You can cook it with the whites in a double boiler (not optional) for Swiss MBC, or alone to add to room temperature beaten whites (in a regular pot on the stove) for Italian MBC.

If a recipe says to use a double broiler, you sure as can use a bowl over water.

Why do you want to use meringue powder? I am not sure if it would work. If you're worried about the eggs, I believe you can use pasteurized whites, but if you're cooking the eggs there's no need to worry.

There is a product on the market usually found in the health food section called "Just Whites" It's a powdered pasuteurized egg white. Usually you can reconstitute it with warm water and use it that way to get the same texture as regular egg whites. Good thing is is you don't have to worry bout the salmonella thing.