Ingredient

Bisque

A bisque is a smooth, rich shellfish soup, and what distinguishes it from any other shellfish soup is that the shells are the main ingredient. They are roasted, simmered and traditionally pounded into the soup rather than thrown away, which is where almost all of the flavour and much of the colour comes from.

Why the shells

Crustacean shells are not inert packaging. They carry a great deal of flavour, and they carry the carotenoid pigments — bound to protein, and dull red-brown until heat releases them — that turn a bisque its characteristic orange.

Two things get that out. Roasting or frying the shells hard browns them and develops flavour through the Maillard reaction, exactly as searing meat does. And cooking them in fat dissolves the carotenoids, which are fat-soluble, so the colour and aroma move into the soup rather than staying locked in the shell.

This is why a bisque made by simmering shells in water tastes thin and looks pale, and why the traditional method insists on both the hard roast and the butter or oil.

The name is said to derive from the two cookings the shellfish receives, though the etymology is disputed. The technique is not.

The method

1. Cook the shellfish briefly — prawns, langoustines, crab or lobster — and pick the meat out. Keep the meat aside for the end. Keep every shell.
2. Roast or fry the shells hard in butter or oil until they are deeply coloured and smell intensely of shellfish. Do not rush this; it is the whole flavour base.
3. Add mirepoix — onion, carrot, celery, fennel — and soften.
4. Add tomato purée and cook it out, then flame or add brandy or Cognac, then white wine, and reduce.
5. Add stock or water and aromatics, and simmer for around forty-five minutes. Longer than that and shells start to give bitterness rather than flavour.
6. Traditionally the shells are then pounded or blitzed with the liquid. If you do this, blend carefully and strain very thoroughly.
7. Pass it through a fine sieve, and then through a fine sieve again, pressing hard to extract everything. Some cooks pass it a third time through muslin. This is what makes a bisque smooth rather than gritty, and it is not a step to skip.
8. Thicken — traditionally with rice cooked in the soup and blended, which is the classical method, or with a little roux or cream.
9. Finish with cream, check the seasoning, add a squeeze of lemon and a dash of cayenne, and warm the reserved shellfish meat through in it.

Decisions and variations

Lobster bisque

The luxurious version. Made from a lobster whose meat is served in it or elsewhere.

Prawn or shrimp bisque

Far cheaper and very good. Shell-on prawns cost little more than peeled and give you the entire flavour base for free.

Crab bisque

Excellent, and brown crab shells give a particularly deep flavour.

Thickening with rice

The classical method — rice simmered in the soup and blended in. Gives body without the flouriness of a roux.

Straining

The single most important technical step. Twice at minimum, through the finest sieve you have.

The shells to keep

Every prawn shell and crab or lobster carcass is a bisque waiting to happen. They freeze perfectly until you have enough.

What goes wrong

• Gritty. Not strained enough, or not strained finely enough. Pass it again.
• Pale and thin. Shells not roasted hard enough, or cooked in water rather than fat.
• Bitter. Shells simmered too long, or the tomato purée burnt.
• Split. The cream boiled. Add it at the end and keep it below a simmer.
• Rubbery shellfish. The reserved meat was cooked twice. Warm it through at the very end and no more.
• Flat. No acid and no heat. Lemon and a pinch of cayenne are both traditional and both do real work.

Common questions