You need 1 large crab, or 1/2 pound of crabmeat (frozen or canned.) Lobster may be used instead.
The crab is cooked first, and the meat cleaned off it, with the white claw meat keep separate. The meat is set aside.
Rice is then boiled in milk until tender.
Both rice and the crab meat (though not the reserved white claw meat) are pressed through a sieve (or these days, liquidized in a blender.) The sieved rice, crab meat and milk are recombined, then a light stock (such as chicken stock) is added, seasoned with salt, pepper, and anchovy. The claw meat pieces and some cream are added and the soup is gently re-heated — it must not be allowed to boil at this stage.
Some like to serve the soup room-temperature, or chilled even. Most people, though, it seems, prefer it hot.
Crab bisque in North America evolved from Partan Bree, brought over by Scottish settlers.
The inclusion of rice is odd, as rice isn’t grown in Scotland.
A Dr William Fullerton of Ayrshire, whose father had been in the East India Company, made his fortune in the latter half of the 1700s trading in Patna rice, and later named the mining town of Patna, Scotland, which he founded, after the Indian city of the same name.
It may be that this recipe, with rice in it, dates from that period. Thus, the recipe as we have it now isn’t that old; it would date only from time when trade made rice commonly available in Scotland.
“Parten” in Scots Gaelic means “crab” (edible crab, “Cancer pagurus”); “bree” in Lowland Scots (“brigh” in Gaelic) means “broth”, brew, liquor, essence [Mackay, Charles. The Gaelic Etymology of the Languages of Western Europe and More. Ludgate Hill: N. Trübner and Co. 1877.]
“Parten” is also used to mean “crab” in Cornish, though a different species (“Carcinus maenas”). [ Courtney, Margaret Ann. Glossary of Words in Use in Cornwall. Ludgate Hill. Trübner & Co. 1880, page 76.]