You know how I said in my notes for the eight-yolk gold cake that I wasn’t going to make this? I lied. I was out of icing sugar to make the glaze I had in mind, so when I found a carton of pasteurized egg whites in my fridge, I decided to give it a whirl since this icing recipe calls for heating them in a double boiler anyway.
I’ve always heard that pasteurized egg whites can’t whip up into as tall and fluffy a meringue as fresh — something about the heat partially cooking the proteins and preventing them from stretching, or something like that. Given the success of this recipe, I might do some experiments of my own to see how accurate that information was.
The original recipe is from The Joy of Cooking, reproduced without changes apart from using my own wording. When I made the icing for today’s gold cake, however, I added the zest of a Meyer lemon as well as its juice, and omitted the cream of tartar since that’s just an acidic ingredient meant to help stabilize the egg. It ended up tasting like a gently sweet lemon marshmallow, which was precisely what I was aiming for.