Chef H made it look so easy, but I found out otherwise. As I was making it for the first time this morning, I found it quite difficult to get the consistency of the chocolate mousse right.
We were supposed to make a full-size cake and a plated dessert of the Marquise, but I could only manage to complete the full-size cake in the given time of 2.5 hours. I had no time to plate the mini dessert at all. My other mistakes were the overworking of the mousse (resulting in a slightly grainy texture), and the temperature of the glaze on top was incorrect. The glaze should have been a touch warmer and more liquid, so that it covers the cake more evenly.
This was what my Marquise au Chocolat looked like at the time I presented it to Chef N:

It really was the best I could manage on the day, and that's all I can ask for from myself.
Chef N said I had nice ideas for decorating the cake, but that I will need to correct the mistakes I made in the making of the cake. Oh well, I live and learn...
Basically, there's nothing else to do but practice (and gain experience). I guess I will have to work faster in the future, but I worry that my attempts to work faster will result in more mistakes, so I will have to be very careful. I will have to review what I did today and come up with a plan for next time. I really do like this cake a lot and I want to make it well.
Anyway, I am heading back to class this afternoon to watch the chef demonstrate the making of the croquembouche, which we will have to make on Wednesday morning.