To a Dutch oven or large stock pot, add shrimp shells, onion, carrot, celery, and salt. If desired, tie parsley stems, thyme, garlic, bay leaf and peppercorns in a sachet or add loosely to the pot (see note 4). Add cold water to cover.
Over medium-high heat, cover and bring to boil. Reduce heat and simmer uncovered (bubbles should barely break the surface at irregular intervals) for 20 minutes.
Strain the broth through a fine-mesh strainer or cheesecloth. Chill covered in the refrigerator, then divide the broth into freezer-safe containers (leaving at least 1/2-inch for expansion), label, and freeze.
Shrimp shells: You'll need 4 cups of shrimp shells from 2 pounds of shrimp for this recipe. But you can gather it in batches: save uncooked shrimp shells in a plastic bag in your freezer until you have enough. Technically, you can make stock with cooked shells, but the flavor will be weaker.
Cold water: Always start with cold water. This helps keep the broth clear, not cloudy. The amount of water used and the length of simmering time will determine the intensity of the broth.
Vegetables: Some cooks save old vegetable trimmings to add to their broth. I prefer to start with new, fresh vegetables because I think the broth will taste better. So yes, we peel the carrots, and save your vegetable scraps for composting!
Herbs and spices: A sachet is a fancy term for parsley stems, thyme, bay leaves, peppercorns, and optionally, garlic or cloves, tied up in a piece of cheesecloth with twine. You could also use a tea ball or loose leaf tea bag to hold them. It makes it easier to pull these small ingredients out of the broth later. Or, you can just add everything straight to the pot since you strain the broth at the end.
Yield: This recipe makes 4 cups (1 quart) shrimp stock.
Storage: Store shrimp stock in the refrigerator and use within 4 days.
Freezer: Divide the stock into freezer-safe containers (I like to use 16-ounce glass jars) and leave 1/2-inch head space for expansion. Label and date, then freeze for up to 3 months. Thaw overnight in the refrigerator.
Shrimp stock vs. broth: Technically, stock is made with just bones (or shells), while broth is made with the bones and meat.
Seafood stock: Lobster bodies (lucky you!) and crab bodies can also be added to make a fantastic seafood stock.