Basically, you put all of your leftover shells in a big pot, cover them with water and add flavoring ingredients, like onion and bay leaf.
I don't stress about having all of the right ingredients. I use what I have on hand at the time.
You can freeze the shells and do this another day, if you don't feel like doing it after the meal.
---Barbara
Seafood Stock
leftover lobster shells and shrimp shells
water to cover
1 bay leaf
1 onion, cut into quarters, papers left on
2 T. Old Bay seasoning
handful of black peppercorns, about 20
a carrot, if you have it, scraped and cut into large chunks
Bring the mixture to a boil, then turn it down to very low, cover, and simmer for 2-3 hours.
Cool for about 1/2 hour.
Then, put a large mesh strainer on top of a stock pot large enough to hold the liquid.
Pour the shells mixture into the strainer, and press the solids to release the flavors.
Remove the strainer and discard the shellfish and onion, etc.
Taste the stock. It shouldn't be too salty, but it should taste fishy.
If it seems too thin and watery, you can put it back on the stovetop and simmer again, uncovered, for another hour or two. Skim off any foam that comes to the top.
Cool.
Then, strain again as you pour into containers for freezing.
Label or you'll wonder what the heck it is.
---Barbara