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How to make shellfish stock

How to make shellfish stock

As shellfish are generally quite expensive, it makes sense to be using up every last part of the crustacean. The shells and legs (once meat has been extracted where possible) of lobsters, crabs, crayfish, langoustines and prawns impart a lot of rich flavour – especially after they're roasted. The heads also contain precious juices, and if you’re not keen on the idea of sucking on them at the dinner table, they should without a doubt be saved for stock.

To make shellfish stock, all you need is shells, vegetables, aromatics and water. How you prepare the shells will have an impact on the final flavour, so it's important to take a little time to roast them beforehand.

Preparing the shells

If you have some shellfish but don’t have time to make stock or want to save the shells up to make a bigger batch, you can break them down into smaller pieces and freeze until ready to use. You can also save the shells after they have been cooked and served – not every diner is meticulous when it comes to scraping out every last bit of meat, so you’re likely to be left with extra tasty morsels to flavour your stock with. Just make sure the shells are collected up and refrigerated or frozen straight after.

While some more old-school recipes require the whole crustacean including its meat, this is a touch extravagant and seems wasteful of the delicate and tender flesh of, say, lobster or langoustine. Carefully shell crustaceans and keep the meat separate from the shells to be cooked and eaten separately. Rinse any shells which may be hiding grit or sand (this is particularly important with crabs) and break down larger shells into smaller pieces. This gives them a larger surface area, which touches the bottom of the pan and caramelises, creating more flavour. The easiest way of doing this is by bashing the shells with a rolling pin in a deep pan or wrapped in a clean cloth.

Compared to fish stock, which has a light, almost perfumed flavour and should be clear in colour, shellfish stock has a rich, deep flavour and is red (due to the shells). As we are after a more robust flavour for shellfish stock, the shells are roasted first to help achieve a deeper flavour. Interestingly, the particles in crustacean shells are not only water soluble but fat soluble too, meaning frying the shells in a fat such as oil or butter before adding water is going to carry over from the pan to your finished stock.

Vegetables and aromatics

When it comes to aromatics, herbs and spices, the same principle of enhancing that deep, caramelised flavour is applied. Sherry or more commonly brandy is added instead of (or as well as) white wine, which adds notes of caramel. As with a dark chicken or veal stock, tomato purée is added for a rich umami undertone and deeper colour. The usual onions, celery and garlic are used with the addition of carrots (which are omitted from fish stock) to boost that sweet flavour and again help achieve a nice deep orange-red colour. Vegetables are best sliced finely to produce more surface area to caramelise. Aniseed ingredients such as fennel and fennel seeds, dill, tarragon and chervil are all common additions which complement the fresh flavour of the sea. A sheet of kombu seaweed can also be added for a mineral-rich hit of umami.

Seasoning

As with all stocks, be careful with seasoning; this stock is cooked for two or three hours, over which time the flavour will intensify and potentially make it too salty. It is always best to leave salting until the end so you know you are happy with the final flavour.

The recipe below makes around a litre of incredibly flavourful stock. The shellfish shells can be made up of langoustines, prawns, crabs or lobsters, and can be precooked or, in the case of langoustines and prawns, peeled from the raw shellfish.

1
Heat a tablespoon of the oil and the butter in a large stock pot. Add the shells (and any juices that have leaked out of them) and cook over a medium heat for 10–15 minutes, stirring to avoid sticking. The shells should be in one layer on the bottom of the pan to enable proper caramelisation, so work in batches if you need to. If you are using langoustines or prawns, use a rolling pin to crush the heads open. Once nicely coloured, transfer the shells to a bowl
2
Deglaze the pan to collect up all the delicious bits stuck to the bottom. Do this by turning the heat up high, then add about 50ml of the brandy. Turn the heat back down and use a spatula to scrape the pan clean. Tip these juices into the bowl of shells
3
Add the remaining oil and, once hot, add the chopped vegetables and smashed garlic. Cook for about 10 minutes until caramelised, stirring to avoid any burning (which would impart a bitter flavour)
4
Add in the tomato puree and cook out for 2 minutes
5
Add the shells back into the pot along with the delicious juices. Pour in the remaining brandy and reduce by half
6
Top up with water to about 3cm above the shells. Bring to the boil and then skim off the scum which rises to the top using a ladle
7
Add the coriander seeds, bay leaves, thyme and any other herbs you choose to use and simmer the stock uncovered for 2–3 hours. Make sure the stock stays at a gentle simmer rather than a rolling boil, and periodically skim off impurities floating on the surface
8
Once ready, place a colander over a large bowl and line with muslin or a thin, clean tea towel. Carefully pour the pan's contents into the colander. Use the back of a ladle to crush the shells, making sure you extract every last bit of stock
9
You can now either return the stock to the pan and reduce further, or chill. The stock will keep for 2–3 days in the fridge or freeze for up to 3 months

How to use shellfish stock in cooking

This highly aromatic stock can be reduced down a little and finished with a spoonful of cream or crème fraîche to create a simple yet stunning bisque. Adding the dairy gives it a velvety texture and mellows out the intensely sweet flavour. Other popular seafood dishes such as paella, risotto, gumbo or chowder are amplified ten times over by a top-quality shellfish stock. The classic French recipe for sauce Américaine follows a similar method to shellfish stock, but with the addition of fresh tomatoes and is flavoured with a dash of cayenne pepper. It is traditionally served with lobster.

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Shellfish demi-glace
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Shellfish glace

Shellfish stock can be reduced right down to make a flavourful and glossy sauce to accompany any fish or seafood. A stock reduced by half is known as demi-glace (demi meaning half in French), and a stock reduced by 80–90% is called a glace. Reducing the stock intensifies flavour and naturally thickens it (without having to use any kind of thickening agent). Turning shellfish stock into a glace is also a good way of storing your stock; once it's reduced right down it should solidify as it cools. You can then portion the glace into ice cube trays to keep in the freezer. By doing this you're essentially creating your own high-quality stock cube; simply dissolve the glace in water to turn it back into shellfish stock.

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How to make shellfish stock

 
 

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