Q: I am planning a shrimp dish which is basically a casserole of black tiger shrimp layered with thin slices of 2 lemons and 1 onion. Over this is poured a butter and herb mixture and then the casserole is cooked in the oven at 400 degrees for 20 minutes. Some cookbooks say that raw shrimp should be cooked in the shell so as not to dry them out. Is it necessary to leave the shells on to cook shrimp or could we shell them before hand?-- Cy S.
Raw shrimp may be cooked either in the shells, or peeled. While leaving the shell on may prevent some surface drying, it also lessens the degree to which the shrimp can absorb any seasoning or flavors that may be used. Depending on the recipe, this may or may not be desirable.
For a dish such as the casserole you describe, you could use shrimp either in the shell or peeled. In this dish you want the shrimp to be infused with the other flavors, so I would be inclined to use peeled shrimp and toss them in the butter/herb mixture before assembly of the casserole, to help keep them from drying out at such a high temperature. Not only will the shrimp be more flavorful, eating them will be less messy.
For a more complex dish, you may wish to leave the shells on. That way, the shrimp will have a more distinct taste from all of the other flavors. When shrimp are used in jambalaya, curries or stews, pre-cooked shrimp can be added towards the end and cooked on low until they are just heated through.