It sounds like the sugar was measured incorrectly and too much was added. Were you scooping condensed sugar out of the bag or spooning fluffed sugar into the measuring cup and leveling off? It makes all the difference. Also – dry frosting can be fixed by adding a splash of milk to moisten it up a bit.

Hi Katherine,
I would avoid the marshmallow altogether. I don’t see that turning out as it will change the consistency of the frosting & change its spreadability. But you can use just water, non-dairy coffee creamer, evaporated milk or coconut milk as a substitute for the milk. This should allow you to leave the cake out a bit longer.

Hi Katherine,
I’m not sure if the cake mix brands heat-treat their ingredients prior to packaging. So if this is a concern to you, feel free to do so. You can heat treat it by spreading on a baking sheet & placing in a 350-degree oven for 5 minutes. I don’t personally do this as it is not something I am at all concerned about.

I usually leave the cake/frosting out for 2-3 hours so that it can be enjoyed at room temperature. But I keep it refrigerated when storing the leftovers. The basic rule for frosting is that the small amount of milk in this recipe is stabilized by a large amount of sugar & therefore considered safe at room temperature for two to three days. Always refrigerate any cake with a frosting that contains eggs or egg whites, or one that has whipped-cream frosting or any type of filling — be it whipped cream, custard, fruit or mousse. Buttercream made with cream cheese, however, is not safe to leave out and should be refrigerated. While none of these apply to this particular frosting recipe, keep in mind that warm humid weather can create a melted mess. A lot of this will be basic common sense based on your climate. If you live in a place that is overly humid, hot or dry, the cake/frosting will be best when kept refrigerated.

Many thanks ?