Seperate but do not peel garlic and roast for 1hr in 1 tablespoon of olive oil.
After the garlic is done, saute onions for 5 minutes in olive oil, put 4 cups of stock in pot. Add the clams and let cook 7-10 minutes, until the shells are all open. After they are open, add the peeled roasted garlic, the juice from 2 limes, salt, pepper and the optional minced jalapeno pepper. Serve hot with chopped cilantro on top.