How do you make hot chocolate for 30 with a hot plate?

In a conference room?

Well, it depends on how big the hot plate is! It would be easier to make the hot chocolate in a crock pot and spoon it out with a ladle. Everybody knows someone with a crock pot! I'm sure you could borrow a few, because it sounds like you would need more than one.

When you say hot plate, I think about those little single cup sized things. If your hot plate is very large, of course this accomodates a large pot , aproximating the size and heating method of a crock-pot.

For 30 people, you would need at LEAST 30 cups of hot chocolate. One should always have more than needed so I would make about 3 gallons worth of hot chocolate.

http://busycooks.about.com/od/beveragere...
http://www.cdkitchen.com/recipes/recipet...

Get a very large kettle.

I'm going to assume your conference room has a coffee maker....

Just run the water through the coffee maker (no coffee, obviously). Fill a basket with individual hot chocolate packets ( you could use different flavors!) and even tea bags. People could then make their own. And don't forget to offer peppermint sticks!!!!