You can make the cookie ahead and leave it covered at room temperature for a couple of days. Frost and top just before serving.
*Lots of options for "frosting" the cookie:
-Vanilla frosting like Simple Mills
-Vanilla frosting + plain softened cream cheese mixed together
-Whipped cream or non-dairy whipped topping (it's one of the unhealthy things I think is so tasty for some reason!)
-Softened cream cheese sweetened (instructions in recipe)
-Strained, sweetened Greek yogurt (see below)
-Softened vanilla ice cream (must be eaten right away obviously!)
To strain Greek yogurt line a colander with a clean, thin kitchen towel, such as a flour sack towel. Spoon the yogurt into the towel, cover, and refrigerate at least 3 to 4 hours. The yogurt will be the consistency of cream cheese. You can even replace the towel after 4 hours and strain a second time, for an even thicker consistency. Not quick, but worth knowing how to do!