I’m making a marshmallow icing to top a high hat cake, but it isn’t coming to stiff peaks no matter the amount of chilling and whipping. How can I get stiff peaks?
If you have even the tiniest amount of fat or egg yolk (which is high in fats) in your bowl or on your whip, or even in the pot in which you cooked the sugar solution, you will never achieve stiff peaks in any sort of meringue. Any meringue is predicated on linking together long molecules of egg protein and even small amounts of fat cause them to literally slip apart. Hence the not-stiff peaks. A good practice before making any meringue is to first wash any and all equipment in hot water with soap and rinse it all very well.
It's also very easy to get a small amount of yolk, which is very high in fat, in with the whites when separating the eggs. Not a marshmallow maker myself, but generally chilling is not helpful with egg whites.
Sorry, this was pretty redundant, don't know what's happening to my reading retention.