The flourless choc cake with meringue topping recipe looks great for what I have in mind, but my questions are

can it be made in advance and still remain crispy,
can it be made in a large quantity in an oven dish, enough for 45 people,
and do you have any suggestions for decorating the top with something suitable for a 21st birthday.
I was rather hoping for something that included cream perhaps, and could be made to look spectacular. Any other suggestions?