Baking question.

[kentauros]

3. However, in this case, it's an icing and it isn't cooked.

From the link given, the ingredients are only mixed together and nothing is heated.

The milk (and the cornstarch) is there to prevent the sugar from forming crystals due by adding fat content. Sugar is a natural preserver so long as the main ingredient is sugar and the moisture content is kept low. That's why candies hardly ever spoil.

If still worried about spoilage due to the milk content, refrigerate or freeze them. The only drawback here is from "sugar bloom" or when moisture collects on the surface and sugar dissolves. As this process repeats, it builds up into a white coating. Airtight wrapping prevents this from occurring.